Lubricant composition for internal combustion engines

Abstract

To provide a lubricant composition for an internal combustion engine which can achieve both reduction in dynamic viscosity and low evaporation property in a low temperature region at high levels.SOLUTION: A lubricant composition for an internal combustion engine contains lubricant base oil and a viscosity index improver, wherein the lubricant base oil satisfies a condition that a dynamic viscosity at 100°C is 2.7 mm2 / s or more and 4.0 mm2 / s, a condition that an evaporation loss amount of lubricant base oil determined by the NOACK evaporation test under conditions of 250°C and 1 hour is 34.0 mass% or less, a condition that ester base oil is not contained as a base oil component as a component, and a condition that a specific amount of a specific base oil component as a component is contained, and the viscosity index improver is poly(meth)acrylate.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a lubricating oil composition for internal combustion engines. [Background technology]

[0002] Conventionally, various compositions of lubricating oils for internal combustion engines have been studied in order to obtain the desired performance. As such a lubricating oil composition for internal combustion engines, for example, Japanese Patent Application Publication No. 2022-22491 (Patent Document 1) describes a lubricating oil composition comprising (A) a base oil and (B) a (co)polymer, wherein the NOACK evaporation rate measured at 250°C for 1 hour is 25 mass% (mass%) or more and less than 40 mass%, and the (B) component, having a weight-average molecular weight (Mw) of 100,000 to 1,000,000, is contained in an amount of 1.0 to 10 mass% of the total mass of the lubricating oil composition, and the kinematic viscosity of the (A) base oil at 100°C is 2.5 to 3.5 mm². 2 A lubricating oil composition is disclosed, which contains a fraction derived from component (A) having a viscosity of / s, satisfying specific conditions for high-temperature high-shear viscosity, and having a boiling point in the range of 350°C to 400°C, in an amount of 40 to 98 mass% of the total mass of the lubricating oil composition.

[0003] Furthermore, Japanese Patent Publication No. 2022-22996 (Patent Document 2) describes a lubricating oil composition comprising (A) a base oil and (B) a (co)polymer, wherein the NOACK evaporation rate measured at 250°C for 1 hour is 25 mass% or more and less than 40 mass%, and the composition contains 0.5 to 6 mass% of the total mass of the lubricating oil composition, with component (B) having a weight-average molecular weight (Mw) of 100,000 to 1,000,000, and a kinematic viscosity at 100°C of 6.1 mm². 2 / s or more 9.3mm 2 A lubricating oil composition is disclosed, which contains 20 to 60 mass% of the total mass of the lubricating oil composition a fraction derived from component (A) having a viscosity of less than / s, satisfying specific conditions for high-temperature high-shear viscosity, and having a boiling point in the range of 350°C to 400°C.

[0004] However, conventional lubricating oil compositions for internal combustion engines, such as those described in Patent Documents 1 and 2, were not always sufficient in terms of achieving both low kinematic viscosity at 40°C, which is an indicator of kinematic viscosity in the low-temperature range including ambient temperature, and low evaporation at a high level. In the field of lubricating oil compositions for internal combustion engines, there is a need for the emergence of lubricating oil compositions for internal combustion engines that can achieve high levels of both low kinematic viscosity and low evaporation at low temperatures, which are two conflicting performance characteristics. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2022-22491 [Patent Document 2] Japanese Patent Publication No. 2022-22996 [Overview of the project] [Problems that the invention aims to solve]

[0006] This invention has been made in view of the problems of the prior art described above, and aims to provide a lubricating oil composition for internal combustion engines that makes it possible to achieve both low viscosity and low evaporation in the low-temperature range at a high level. [Means for solving the problem]

[0007] As a result of diligent research to achieve the above objective, the present inventors have developed a lubricating oil composition for internal combustion engines containing a lubricating oil base oil and a viscosity index improver, wherein the kinematic viscosity of the lubricating oil base oil at 100°C is 2.7 mm². 2 / s or more 4.0mm 2 / s or less; an evaporation loss of the lubricating base oil determined by a NOACK evaporation test under conditions of 250°C for 1 hour of 34.0 mass% or less; the lubricating base oil contains no ester base oil as a constituent base oil component; the lubricating base oil contains, as a constituent component, at least one base oil component satisfying the following specific conditions (I) to (IV); the lubricating base oil contains the base oil component(s) satisfying the following specific conditions (I) to (IV) in a total amount of 30 mass% or more based on the total amount of the lubricating base oil; and the viscosity index improver is poly(meth)acrylate. The inventors have found that this allows the resulting lubricating oil composition to achieve both a low kinematic viscosity in low-temperature regions and low evaporation property at a high level, and have thus completed the present invention.

[0008] That is, the present invention provides the following embodiments.

[0009] [1] A lubricating oil composition for internal combustion engines containing a lubricating base oil and a viscosity index improver, wherein the lubricating base oil has a kinematic viscosity at 100°C of 2.7 mm 2 / s or more and 4.0 mm 2 / s or less, the lubricating base oil has an evaporation loss determined by a NOACK evaporation test under conditions of 250°C for 1 hour of 34.0 mass% or less, the lubricating base oil does not contain an ester base oil as a constituent base oil component, the lubricating base oil contains, as a constituent component, a base oil component satisfying the following conditions (I) to (IV): [Condition (I)] a kinematic viscosity at 100°C of 1.8 mm 2 / s or more and 3.9 mm 2 / s or less, [Condition (II)] a kinematic viscosity at 40°C of 5.5 mm 2 / s or more and 20.0 mm 2 / s or less, [Condition (III)] an evaporation loss of the base oil component determined by a NOACK evaporation test under conditions of 250°C for 1 hour of 50.0 mass% or less, [Condition (IV)] The following formula (1): X = Y × 4.6 + Z (1) (In the formula, Y represents the kinematic viscosity of the base oil component at 40°C, and Z represents the evaporation loss of the base oil component determined by the NOACK evaporation test under conditions of 250°C for 1 hour.) The calculated value X obtained by this method must be 100 or less. It contains at least one base oil component that satisfies the following conditions: The lubricating oil base oil contains a total of 30 mass% or more of base oil components that satisfy the above conditions (I) to (IV) on a basis of the total amount of the lubricating oil base oil, and A lubricating oil composition for internal combustion engines, wherein the viscosity index improver is poly(meth)acrylate.

[0010] [2] The lubricating oil composition for internal combustion engines according to [1], wherein the lubricating oil base oil contains a total of 50 mass% or more of base oil components that satisfy the above conditions (I) to (IV) on a basis of the total amount of the lubricating oil base oil.

[0011] [3] The lubricating oil composition for internal combustion engines according to [1] or [2], wherein the evaporation loss of the lubricating oil base oil, as determined by a NOACK evaporation test under the conditions of 250°C for 1 hour, is 31.0 mass% or less.

[0012] [4] The lubricating oil composition for internal combustion engines according to any one of [1] to [3], wherein the lubricating oil base oil comprises at least one mineral oil-based base oil as a base oil component constituting the lubricating oil base oil. [Effects of the Invention]

[0013] According to the present invention, it is possible to provide a lubricating oil composition for internal combustion engines that can achieve both low viscosity and low evaporation at low temperatures. [Brief explanation of the drawing]

[0014] [Figure 1] This graph plots the relationship between the kinematic viscosity at 40°C and the NOACK (250°C, 1 hour) evaporation loss for 18 different base oil samples. [Modes for carrying out the invention]

[0015] The present invention will be described in detail below with reference to its preferred embodiments. In this specification, unless otherwise specified, the notation "X~Y" for numerical values ​​X and Y means "X or greater and Y or less". If a unit is attached only to the numerical value Y in such notation, that unit shall also apply to the numerical value X.

[0016] [Lubricant composition for internal combustion engines] The present invention is a lubricating oil composition for internal combustion engines comprising a lubricating oil base oil and a viscosity index improver, The lubricating oil base oil has a kinematic viscosity of 2.7 mm at 100°C. 2 / s or more 4.0mm 2 Items less than or equal to / s The aforementioned lubricating oil base oil has an evaporation loss of 34.0 mass% or less, as determined by a NOACK evaporation test under the conditions of 250°C for 1 hour. The aforementioned lubricating oil base oil does not contain ester base oil as a constituent base oil component. The aforementioned lubricating oil base oil has the following constituent conditions (I) to (IV): [Condition (I)] Kinematic viscosity at 100°C is 1.8 mm 2 / s or more 3.9mm 2 It must be less than or equal to / s. [Condition (II)] Kinematic viscosity at 40°C is 5.5 mm 2 / s or more 20.0mm 2 It must be less than or equal to / s. [Condition (III)] The evaporation loss of base oil components, as determined by the NOACK evaporation test under the conditions of 250°C for 1 hour, must be 50.0 mass% or less. [Condition (IV)] The following formula (1): X = Y × 4.6 + Z (1) (In the formula, Y represents the kinematic viscosity of the base oil component at 40°C, and Z represents the evaporation loss of the base oil component determined by the NOACK evaporation test under conditions of 250°C for 1 hour.) The calculated value X obtained by this method must be 100 or less. It contains at least one base oil component that satisfies the following conditions: The lubricating oil base oil contains a total of 30 mass% or more of base oil components that satisfy the above conditions (I) to (IV) on a basis of the total amount of the lubricating oil base oil, and The viscosity index improver is characterized by being a poly(meth)acrylate.

[0017] In this specification, all base oils contained as constituent components of lubricating oil base oil are referred to as "base oil components," and a composition of base oils consisting of all base oil components contained as constituent components (however, the term "composition" here includes cases where it consists of only one type of base oil component) is referred to as "lubricating oil base oil." Thus, in this specification, when a lubricating oil composition contains only one type of base oil component, the mixture consisting of only that one type of base oil component (the total base oil in the lubricating oil composition) is referred to as "lubricating oil base oil," and when the lubricating oil composition contains multiple base oil components, the mixture of base oils consisting of those multiple base oil components (the total base oil in the lubricating oil composition) is referred to as "lubricating oil base oil," and the base oils contained as constituent components in that lubricating oil base oil are referred to as "base oil components." Furthermore, in this specification, "NOACK evaporation test under conditions of 250°C for 1 hour" refers to a test in accordance with ASTM D5800.

[0018] Furthermore, the lubricating oil base oil (total base oil) according to the present invention has a kinematic viscosity of 2.7 mm at 100°C. 2 / s or more 4.0mm 2 It must be less than / s. The kinematic viscosity of such a lubricating oil base oil at 100°C is 2.9 mm². 2 / s or more and 3.9 or less (more preferably 3.0 mm) 2 / s or more 3.9mm 2 / s or less, more preferably 3.0 mm 2 / s or more 3.7mm 2 / s or less, particularly preferably 3.2 mm 2 / s or more 3.7mm 2 / s or less, most preferably 3.3 mm 2 / s or more 3.7mm 2It is more preferable that the kinematic viscosity of the lubricating oil base oil at 100°C is 4.0 mm². 2 By having a viscosity of less than / s, excellent fuel efficiency can be achieved. Furthermore, the kinematic viscosity of the lubricating oil base oil at 100°C is 2.7 mm². 2 A value of 1 / s or higher ensures the formation of an oil film at the lubrication points and further reduces evaporation loss of the lubricating oil composition.

[0019] Furthermore, the lubricating oil base oil (whole base oil) according to the present invention must have an evaporation loss (NOACK (250°C, 1 hour) evaporation loss) of 34.0 mass% or less (preferably 31.0 mass% or less) as determined by a NOACK evaporation test (hereinafter sometimes simply referred to as "NOACK (250°C, 1 hour)") conducted under conditions of 250°C, 1 hour in accordance with ASTM D5800. Moreover, it is more preferable that the NOACK (250°C, 1 hour) evaporation loss of such a lubricating oil base oil (whole base oil) is 16.0 to 31.0 mass% (more preferably 18.0 to 29.8 mass%, and particularly preferably 20.4 to 24.8 mass%). By keeping the NOACK (250°C, 1 hour) evaporation loss below the above upper limit, a high level of low evaporation performance is achieved. On the other hand, by setting the NOACK (250°C, 1 hour) evaporation loss above the aforementioned lower limit, an even greater effect tends to be obtained in terms of improving fuel efficiency by reducing the viscosity of the lubricating oil composition.

[0020] Furthermore, the lubricating oil base oil (total base oil) according to the present invention has a kinematic viscosity of 18.0 mm at 40°C. 2 / s or less (more preferably 9.8 mm) 2 / s or more 16.6mm 2 / s or less, more preferably 9.8 mm 2 / s or more 15.8mm 2 / s or less, particularly preferably 12.5 mm 2 / s or more, 14.9mm 2 / s or less, most preferably 12.5 mm 2 / s or more 12.8mm 2 It is preferable that the kinematic viscosity of such lubricating oil base oil at 40°C is 18.0 mm².2 By setting the kinematic viscosity to less than / s, it becomes possible to further reduce the kinematic viscosity of the final composition in the low-temperature range. Furthermore, by setting the kinematic viscosity of the lubricating oil base oil at 40°C to above the aforementioned lower limit, it becomes possible to form an oil film more efficiently at low-temperature lubrication points.

[0021] In this specification, "kinematic viscosity at 40°C" and "kinematic viscosity at 100°C" refer to values ​​measured in accordance with ASTM D-445, respectively. In the following, the "kinematic viscosity at 40°C" of the base oil or composition will be referred to simply as "40°C kinematic viscosity," and the "kinematic viscosity at 100°C" of the base oil or composition will be referred to simply as "100°C kinematic viscosity."

[0022] The lubricating oil base oil (total base oil) according to the present invention preferably contains 3.2 mass% or less (more preferably 2.0 mass% or less, and even more preferably 1.7 mass% or less) of components with a boiling point of 330°C or less, based on the total amount of the lubricating oil base oil. By keeping the content of such components with a boiling point of 330°C or less below the above upper limit, evaporation loss during use can be further reduced, and an even higher effect in terms of low evaporation can be obtained. The content of the above components in the lubricating oil base oil can be determined by calculating the content ratio of components with a boiling point of 330°C or less relative to the total amount of the lubricating oil base oil from the gas chromatogram obtained by performing a gas chromatography distillation test on the lubricating oil base oil using the following condition (A) (for convenience, the gas chromatography distillation test using such condition (A) will be referred to as "gas chromatography distillation test (A)" below). The gas chromatography distillation test (A) is a test in which the conditions and other factors have been appropriately modified to obtain the desired data, based on the test method described in JIS K2254.

[0023] [Conditions for gas chromatography distillation test (A)] Measuring device: Shimadzu Corporation, product name: GC-2030 Column: Ultraalloy-1HT (UA-1HT; length 5m, inner diameter (ID) 0.5mm, film thickness 0.1μm: manufactured by Frontier Lab Co., Ltd.) Carrier gas: He (Flow rate: 15 mL / min) Detector: Flame ionization detector (FID) Detector temperature: 400℃ Inlet temperature: Programmable temperature vaporization (PTV) inlet, 40℃~380℃ Column temperature: After holding at 40°C for 6 minutes, the temperature is increased to 380°C at a heating rate of 10°C / minute.

[0024] The lubricating oil base oil (total base oil) according to the present invention has the following constituent conditions (I) to (IV): [Condition (I)] Kinematic viscosity at 100°C is 1.8 mm 2 / s or more 3.9mm 2 It must be less than or equal to / s. [Condition (II)] Kinematic viscosity at 40°C is 5.5 mm 2 / s or more 20.0mm 2 It must be less than or equal to / s. [Condition (III)] The evaporation loss of base oil components, as determined by the NOACK evaporation test under the conditions of 250°C for 1 hour, must be 50.0 mass% or less. [Condition (IV)] The following formula (1): X = Y × 4.6 + Z (1) (In the formula, Y represents the kinematic viscosity of the base oil component at 40°C, and Z represents the evaporation loss of the base oil component determined by the NOACK evaporation test under conditions of 250°C for 1 hour.) The calculated value X obtained by this method must be 100 or less. It must contain at least one base oil component that satisfies the following conditions.

[0025] Thus, the base oil component included in the lubricating oil base oil (total base oil) as an essential component (essential constituent component) has a kinematic viscosity of 1.8 mm at 100°C. 2 / s or more 3.9mm 2 / s or less (more preferably 2.7 mm) 2 / s or more 3.9mm 2 / s or less, more preferably 3.0 mm 2 / s or more 3.9mm 2 The condition (I) must be met, which is less than or equal to / s. By making the kinematic viscosity of such base oil components at 100°C less than or equal to the upper limit, it is possible to improve the fuel efficiency of the composition by reducing viscous resistance, while by making it greater than or equal to the lower limit, it is possible to improve the oil film retention at high temperatures.

[0026] Furthermore, the base oil component included as an essential component in the lubricating oil base oil (total base oil) has a kinematic viscosity of 5.5 mm at 40°C. 2 / s or more 20.0mm 2 / s or less (more preferably 9.8 mm) 2 / s or more 14.6mm 2 / s or less, more preferably 12.8 mm 2 / s or more 15.9mm 2 The condition (II) must be met, which is less than or equal to / s. By keeping the kinematic viscosity of such base oil components at 40°C below the upper limit, it tends to be possible to obtain an even greater effect in reducing the viscous resistance of the composition when operating in a temperature range close to room temperature, thereby improving fuel efficiency.

[0027] Furthermore, the base oil components included as essential components in the lubricating oil base oil (total base oil) must satisfy condition (III), which is that the evaporation loss of the base oil components (NOACK (250°C, 1 hour) evaporation loss), determined by a NOACK evaporation test conducted at 250°C for 1 hour in accordance with ASTM D5800, is 50.0 mass% or less (preferably 33.4 mass% or less, more preferably 24.5 mass% or less). By keeping the NOACK (250°C, 1 hour) evaporation loss of such base oil components below the upper limit, it is possible to achieve a high level of low evaporation. On the other hand, by keeping the NOACK (250°C, 1 hour) evaporation loss above the lower limit, it tends to be possible to obtain an even greater effect in terms of improving fuel efficiency by lowering the viscosity of the lubricating oil composition.

[0028] Furthermore, the base oil components included as essential components in the lubricating oil base oil (total base oil) are given by the following formula (1): X = Y × 4.6 + Z (1) (In the formula, Y represents the kinematic viscosity of the base oil component at 40°C, and Z represents the evaporation loss of the base oil component determined by the NOACK evaporation test under conditions of 250°C for 1 hour.) Condition (IV) must be met, which is that the calculated value X obtained by this method is 100 or less. By setting such a calculated value X to 100 or less, it becomes possible to design a lubricating oil composition that maintains a certain level of evaporation prevention while reducing the kinematic viscosity at room temperature while maintaining equivalent viscosity at high temperatures. Furthermore, such a calculated value X is more preferably 86.8 or less, and even more preferably 84.0 or less, as this yields even greater benefits from a similar viewpoint.

[0029] Here, we will explain equation (1) for determining the calculated value X. Equation (1) was derived as a concept of a calculated value X, which serves as an indicator when designing a lubricating oil composition with excellent fuel efficiency that effectively reduces kinematic viscosity at room temperature, given that a certain level of evaporation prevention and maintenance of (kinematic) viscosity at high temperatures are specified in the formulation design. As shown below, the equation was formulated using a large number of base oil samples, including base oil components (1) to (12) used in the examples, so that it can be applied to all kinds of base oil components. Specifically, first, 18 types of base oils were prepared as samples for determining equation (1), and the kinematic viscosity at 40°C and the NOACK (250°C, 1 hour) evaporation loss of each base oil were measured. Regarding the NOACK (250°C, 1 hour) evaporation loss of base oils, for those with a NOACK (250°C, 1 hour) evaporation loss exceeding 60 mass%, it is not possible to directly measure the NOACK (250°C, 1 hour) evaporation loss using only that base oil. Therefore, three or more samples were prepared, each consisting of a mixture in which the base oil of the measurement target was contained in different ratios with other base oils whose NOACK (250°C, 1 hour) evaporation loss was known. The NOACK (250°C, 1 hour) evaporation loss of each sample was determined, and an estimated value was calculated by obtaining an approximate straight line from these measured values. The relationship between the kinematic viscosity at 40°C and the NOACK (250°C, 1 hour) evaporation loss of each base oil sample obtained in this way is plotted in Figure 1. Furthermore, by focusing on base oil components that enable the realization of a lubricating oil composition that achieves both viscosity-temperature characteristics and evaporation characteristics, rather than just one of these two characteristics, we found that the sum of 4.6 times the kinematic viscosity at 40°C and the NOACK (250°C, 1 hour) evaporation loss (corresponding to the calculated value X) can serve as an indicator of the compatibility of the two characteristics. In this way, we derived equation (1) using a large number of samples. Figure 1 shows the straight line of equation (1) when the calculated value X, which is an indicator of the compatibility of viscosity-temperature characteristics and evaporation characteristics, is 100. Figure 1 also clearly shows the upper and lower limits of conditions (II) and (III), which are necessary for designing a lubricating oil composition with good viscosity-temperature characteristics or evaporation characteristics, using dotted lines.When the calculated value X satisfies the above conditions, a sufficient level of effect can be obtained in terms of suppressing oil consumption due to good evaporation characteristics and improving fuel efficiency due to good viscosity-temperature characteristics.

[0030] Furthermore, it is preferable that the base oil component that satisfies conditions (I) to (IV) above, and is included as an essential component in the lubricating oil base oil (total base oil), further satisfies the condition that the content of a component with a boiling point of 330°C or less (content relative to the total amount of the base oil component) is 2.2 mass% or less (more preferably 2.0 mass% or less, particularly preferably 0.0 mass%). By keeping the content of such a component with a boiling point of 330°C or less below the above upper limit, it is possible to achieve both low viscosity and low evaporability in the low-temperature range of the resulting lubricating oil composition at a high level. The content of such a component with a boiling point of 330°C or less can be determined by performing the "gas chromatographic distillation test (A)" on the base oil component to be used and calculating the content ratio of the component with a boiling point of 330°C or less relative to the total amount of the base oil component from the gas chromatogram obtained.

[0031] Furthermore, the lubricating oil base oil (total base oil) according to the present invention must contain a total of 30 mass% or more of base oil components that satisfy the above conditions (I) to (IV) based on the total amount of the lubricating oil base oil (Note that the description of content as "total of 30 mass% or more" indicates the content of only one type of base oil component that satisfies the above conditions (I) to (IV) if the lubricating oil base oil contains only one type, and the total amount of those components if it contains two or more types). In other words, the total amount of base oil components that satisfy the above conditions (I) to (IV) in the lubricating oil base oil (total base oil) according to the present invention must be 30 mass% or more. Here, it is preferable that the total amount of base oil components that satisfy the above conditions (I) to (IV) in the lubricating oil base oil (total base oil) be 30 mass% or more (more preferably 60 mass% or more, and most preferably 70 mass% or more). By ensuring that the total content of base oil components satisfying the above conditions (I) to (IV) is 30 mass% or more based on the total amount of lubricating oil base oil, it becomes possible to significantly obtain the effects of suppressing oil consumption due to the good evaporation characteristics of the lubricating oil composition and improving fuel efficiency due to the good viscosity-temperature characteristics.

[0032] Furthermore, the lubricating oil base oil (all base oil) according to the present invention must not contain ester base oil as a constituent base oil component. If ester base oil is included in the lubricating oil base oil (all base oil), it becomes impossible to achieve both the suppression of oil consumption and the improvement of viscosity-temperature characteristics (particularly the reduction of kinematic viscosity in the low-temperature range), and it becomes difficult to simultaneously maintain high-temperature oxidation stability at a good level, resulting in a decrease in the performance of the lubricating oil composition.

[0033] Furthermore, such lubricating oil base oil (total base oil) may consist of one type of base oil component, or it may consist of a mixture of multiple (two or more) base oil components. The type of base oil component that makes up such lubricating oil base oil is not particularly limited, as long as it is not an ester base oil, and mineral oil-based base oil or synthetic base oil other than ester base oil can be used as appropriate.

[0034] The mineral oil-based base oil that can be used as the base oil component is not particularly limited, and distillates obtained by atmospheric distillation of crude oil can be used. In addition, lubricating oil fractions obtained by further vacuum distillation of this distillate and then refined through various refining processes can also be used. As refining processes, hydrogenation refining, solvent extraction, solvent dewaxing, hydrogenation dewaxing, sulfuric acid washing, and clay treatment can be combined as appropriate. By combining these refining processes in an appropriate order, a lubricating oil base oil that can be used in the lubricating oil composition of the present invention can be obtained. A mixture of multiple refined oils with different properties obtained by subjecting different crude oils or distillates to different refining process combinations can also be used.

[0035] Furthermore, it is preferable to use a mineral oil-based base oil belonging to Group III in the API classification as the base oil component. API Group III base oils are mineral oil-based base oils with a sulfur content of 0.03 mass% or less, a saturation content of 90 mass% or more, and a viscosity index of 120 or higher. When using API Group III base oils, multiple types of Group III base oils may be used, or only one type may be used. Furthermore, it is also possible to use a mineral oil-based base oil belonging to Group II in the API classification as the base oil component. API Group II base oils are mineral oil-based base oils with a sulfur content of 0.03 mass% or less, a saturation content of 90 mass% or more, and a viscosity index of 80 or more and less than 120. When using API Group II base oils, multiple types of Group II base oils may be used, or only one type may be used.

[0036] Other synthetic base oils besides ester base oils that can be used as the base oil component include poly-α-olefins and their hydrogenates, isobutene oligomers and their hydrogenates, isoparaffins, alkylbenzenes, alkylnaphthalenes, polyoxyalkylene glycols, dialkyldiphenyl ethers, polyphenyl ethers, and mixtures thereof. Among these, poly-α-olefins are preferred. Typical examples of poly-α-olefins include oligomers or co-oligomers of α-olefins having 2 to 32 carbon atoms, preferably 6 to 16 carbon atoms (1-octene oligomers, decene oligomers, ethylene-propylene co-oligomers, etc.) and their hydrogenation products.

[0037] Furthermore, it is preferable that the lubricating oil base oil (total base oil) contains at least one mineral oil-based base oil as a base oil component. That is, it is preferable that such a lubricating oil base oil (total base oil) satisfies the condition that it is not composed solely of synthetic base oils (among them, it is particularly preferable that it does not satisfy the condition that it is not composed solely of Fischer-Tropsch base oil). By making the lubricating oil base oil not composed solely of synthetic base oils (by including at least one mineral oil-based base oil), it is possible to improve fuel efficiency by improving the viscosity-temperature characteristics of the composition, and at the same time, further reduce evaporation loss of the lubricating oil composition. Also, from the same viewpoint, it is preferable that the lubricating oil base oil does not contain (use) synthetic base oils (for example, Fischer-Tropsch base oil) as a base oil component that is a component of the lubricating oil base oil, as this can be used to obtain an even higher effect. Furthermore, in the present invention, from the viewpoint of economic rationality, it is preferable that the base oil component that satisfies the above conditions (I) to (IV) is a mineral oil-based base oil.

[0038] Furthermore, if the lubricating oil base oil (total base oil) contains at least one mineral oil-based base oil in its base oil components, the mineral oil-based base oil content is preferably 87 mass% to 100 mass% and more preferably 95 mass% to 100 mass% based on the total amount of lubricating oil base oil. By setting the mineral oil-based base oil content in the lubricating oil base oil to above the aforementioned lower limit, it is possible to improve fuel efficiency by improving the viscosity-temperature characteristics of the composition, while simultaneously further reducing evaporation losses of the lubricating oil composition.

[0039] Furthermore, in the lubricating oil composition for internal combustion engines of the present invention, the content of the lubricating oil base oil (total base oil) is preferably 70.0 mass% to 95.0 mass%, more preferably 75.3 mass% to 90.0 mass%, and particularly preferably 85.6 mass% to 89.9 mass%, based on the total amount of the lubricating oil composition for internal combustion engines (based on the total amount of the composition). Setting the lubricating oil base oil content above the lower limit allows for even greater effectiveness in terms of the solubility stability of additives compared to the case where it is below the lower limit. On the other hand, setting the lubricating oil base oil content below the upper limit allows for the application of additives, making it easier to adjust properties such as viscosity-temperature characteristics and cleaning stability according to the application.

[0040] Furthermore, the lubricating oil composition for internal combustion engines of the present invention contains a viscosity index improver along with the lubricating oil base oil. Here, "viscosity index improver" means a compound that, when added to the lubricating oil, has the function of reducing the change in viscosity of the lubricating oil due to temperature changes.

[0041] Furthermore, in the present invention, the viscosity index improver must be poly(meth)acrylate (more preferably polymethacrylate). By using poly(meth)acrylate as a viscosity index improver in this way, the viscosity-temperature characteristics can be improved, and by maintaining low viscosity in the low-temperature range while improving viscosity in the high-temperature range, fuel efficiency can be further improved. In this specification, "(meth)acrylate" means acrylate and / or methacrylate, and "poly(meth)acrylate" means a polymer containing acrylate monomer units and / or methacrylate monomer units.

[0042] Furthermore, any of the following types of poly(meth)acrylate (PMA) may be used: dispersed poly(meth)acrylate, non-dispersive poly(meth)acrylate, and comb-type poly(meth)acrylate. There are no particular restrictions, however, comb-type poly(meth)acrylate is preferred from the viewpoint of improving the viscosity-temperature characteristics and increasing the viscosity in the high-temperature range while maintaining a low viscosity in the low-temperature range, thereby further enhancing fuel efficiency.

[0043] Here, "dispersed poly(meth)acrylate" means a poly(meth)acrylate compound having a functional group containing a nitrogen atom, and "non-dispersed poly(meth)acrylate" means a poly(meth)acrylate compound that does not have a functional group containing a nitrogen atom. Furthermore, as the comb-shaped poly(meth)acrylate, known poly(meth)acrylate polymers having a so-called comb-shaped structure (for example, "comb-shaped polymer" described in Japanese Patent Publication No. 2017-101211, "comb-shaped poly(meth)acrylate" described in Japanese Patent Publication No. 2018-177986, "comb-shaped poly(meth)acrylate" described in International Publication No. 2016 / 159006, "viscosity index improver" described in Japanese Patent Publication No. 2017-110196, "(co)polymer (A)" described in Japanese Patent Publication No. 2017-110196, etc.) can be used as appropriate. For example, macromonomers derived from hydrides of polyolefins obtained by copolymerizing butadiene and isoprene can be used as such comb-shaped poly(meth)acrylates.

[0044] Furthermore, the weight-average molecular weight (Mw) of the viscosity index improver is, for example, 10,000 to 1,000,000, preferably 50,000 to 900,000, more preferably 100,000 to 800,000, and even more preferably 150,000 to 600,000. Moreover, the Mw / Mn (weight-average molecular weight / number-average molecular weight) of the viscosity index improver is, for example, 2.3 to 6.0, preferably 2.5 to 5.5, and more preferably 3.0 to 5.0. By keeping Mw / Mn within the above range, the viscosity index can be maintained well. In this specification, the weight-average molecular weight Mw and number-average molecular weight Mn of the viscosity index improver refer to values ​​obtained by gel permeation chromatography (GPC) (molecular weight obtained in polystyrene equivalent), respectively.

[0045] In the lubricating oil composition for internal combustion engines of the present invention, the content of the viscosity index improver in terms of resin content is preferably 0.1 mass% or more and 20 mass% or less (more preferably 1.0 mass% or more and 10 mass% or less, and more preferably 1.5 mass% or more and 3.0 mass% or less) on a basis of the total amount of the composition. By setting the content of the viscosity index improver in terms of resin content to below the above upper limit, it is possible to improve the viscosity-temperature characteristics while maintaining cleanliness. On the other hand, by setting it to above the above lower limit, it is possible to improve the viscosity-temperature characteristics by achieving low viscosity at low temperatures, including the room temperature range, when adjusting the kinematic viscosity at high temperatures to be equivalent. Herein, "content of the viscosity index improver in terms of resin content" means the content of the resin component constituting the viscosity index improver in the lubricating oil composition, and in this specification, "resin component" means a polymer component with a molecular weight of 1,000 or more.

[0046] Furthermore, it is preferable that the lubricating oil composition for internal combustion engines of the present invention does not contain olefin copolymers. If olefin copolymers are included in the lubricating oil composition for internal combustion engines, it becomes impossible to lower the kinematic viscosity in the low-temperature range, which tends to reduce fuel efficiency.

[0047] Furthermore, the lubricating oil composition for internal combustion engines of the present invention may appropriately contain, along with the lubricating oil base oil and viscosity index improver, additives that can be used in lubricating oil compositions for internal combustion engines. Such additives can be any known additives used in lubricating oil compositions for internal combustion engines, and are not particularly limited. However, metal-based detergents, molybdenum-based friction modifiers, ashless friction modifiers, antioxidants, anti-wear agents, dispersants, pour point depressants, anti-emulsifiers, metal deactivators, and defoamers are preferred, and viscosity index improvers, metal-based detergents, molybdenum-based friction modifiers, ashless friction modifiers, antioxidants, anti-wear agents, and dispersants are more preferred (note that the additives listed here are just preferred examples, and the available additives are not limited thereto). Such additives can be used individually or in combination of two or more.

[0048] Furthermore, the lubricating oil composition for internal combustion engines of the present invention preferably contains a metal-based detergent. Examples of such metal-based detergents include calcium-based detergents, magnesium-based detergents, and / or barium-based detergents. These detergents may be over-basicated with boric acid, borates, carbonic acid, or carbonates. As the metal-based detergent, a metal-based detergent having a salicylate group (metal-based detergent having a salicylate structure), a metal-based detergent having a sulfonate group, or a metal-based detergent having a phenate group can be used. It is preferable to use a metal-based detergent having a salicylate group (metal-based detergent having a salicylate structure).

[0049] Furthermore, it is preferable that such metal-based detergents contain magnesium carbonate. Suitable examples of such metal-based detergents include those containing magnesium carbonate and a salicylate group, and those containing magnesium carbonate and a sulfonate group. Such metal-based detergents can be used individually or in combination of two or more (for example, by using one containing magnesium carbonate in combination with a metal-based detergent containing a metal other than magnesium).

[0050] When the lubricating oil composition for internal combustion engines of the present invention contains a metal-based detergent, the specific range of the amount of metal derived from the metal-based detergent is preferably 100 mass ppm (ppm by mass) or more and 2200 mass ppm or less (more preferably 453 mass ppm or more and 1901 mass ppm or less, and even more preferably 1400 mass ppm or more and 1901 mass ppm or less) on a basis of the total amount of the composition. In this specification, unless otherwise specified, the content of each element, calcium, magnesium, sulfur, zinc, boron, phosphorus, and molybdenum, in the oil shall be measured by inductively coupled plasma atomic emission spectrometry (intensity ratio method (internal standard method)) in accordance with JIS K0116. By keeping the amount of metal derived from the metal-based detergent below the above upper limit, the sulfated ash content can be reduced compared to when it exceeds the above upper limit, and the value of the friction coefficient can also be reduced.

[0051] The base number (perchloric acid method) of the metal-based detergent used in the lubricating oil composition for internal combustion engines of the present invention is preferably in the range of 10 mg KOH / g or more and 650 mg KOH / g or less, and more preferably 190 mg KOH / g or more and 400 mg KOH / g or less. In this specification, the base number (perchloric acid method) of the metal-based detergent is the value measured according to JIS K 2501:2003, item 9.

[0052] Furthermore, the lubricating oil composition for internal combustion engines of the present invention preferably contains a molybdenum-based friction modifier. Such a molybdenum-based friction modifier is not particularly limited, and known ones can be used as appropriate. Molybdenum dithiocarbamate (hereinafter sometimes simply referred to as "MoDTC") and dialkylamine salts of molybdate are suitably used. Moreover, such a molybdenum-based friction modifier preferably contains MoDTC, and is particularly preferably MoDTC. By using such a molybdenum-based friction modifier, it is possible to reduce the coefficient of friction. Such a molybdenum-based friction modifier may be used alone, or two or more may be used in any combination in any proportion.

[0053] Furthermore, as the MoDTC, for example, a compound represented by the following formula (A) can be used.

[0054] [ka]

[0055] In the above formula (A), R 1 ~R 4These may be the same or different, and are an alkyl group having 2 to 24 carbon atoms or an (alkyl)aryl group having 6 to 24 carbon atoms, preferably an alkyl group having 4 to 13 carbon atoms or an (alkyl)aryl group having 10 to 15 carbon atoms. The alkyl group may be a primary alkyl group, a secondary alkyl group, or a tertiary alkyl group, and may be linear or branched. Note that "(alkyl)aryl group" means "aryl group or alkylaryl group". In an alkylaryl group, the substitution position of the alkyl group on the aromatic ring is arbitrary. 1 ~X 4 Each is independently either a sulfur atom or an oxygen atom, and X 1 ~X 4 At least one of them is a sulfur atom.

[0056] Examples of molybdenum-based friction modifiers other than MoDTC include molybdenum dithiophosphate, molybdenum oxide, molybdic acid, molybdate salts such as ammonium salts, molybdenum disulfide, molybdenum sulfide, molybdic acid sulfide, and molybdenum-based friction modifiers containing sulfur. It is preferable to use a dialkylamine salt of molybdate as a molybdenum-based friction modifier other than MoDTC.

[0057] When the lubricating oil composition for internal combustion engines of the present invention contains a molybdenum-based friction modifier, it is preferable that the amount of molybdenum derived from the molybdenum-based friction modifier is 50 masssppm or more and 2000 masssppm or less (more preferably 300 masssppm or more and 1800 masssppm or less, even more preferably 500 masssppm or more and 1000 masssppm or less, and particularly preferably 600 masssppm or more and 850 masssppm or less) on a basis of the total amount of the composition. By having a molybdenum content above the lower limit, fuel efficiency can be improved compared to when it is below the lower limit. Furthermore, by having a molybdenum content below the upper limit, the storage stability of the lubricating oil composition can be improved compared to when it exceeds the upper limit. The amount of molybdenum in the oil shall be measured by inductively coupled plasma atomic emission spectrometry (intensity ratio method (internal standard method)) in accordance with JPI-5S-62.

[0058] Furthermore, the lubricating oil composition for internal combustion engines of the present invention preferably contains an ashless friction modifier. In this specification, an ashless friction modifier means a friction modifier that does not contain metal elements. By including such an ashless friction modifier, the friction coefficient of the composition can be reduced. Such an ashless friction modifier is not particularly limited, and known ones can be used as appropriate. For example, ashless friction modifiers containing nitrogen, or ashless friction modifiers consisting of dithiocarbamates, zinc dithiocarbamates, disulfides, polysulfides, sulfurized olefins, and sulfurized oils can be used as appropriate. In addition, one type of such ashless friction modifier may be used alone, or two or more types may be used in any combination in any proportion. Other types of ashless friction modifiers may also be included as appropriate.

[0059] Furthermore, as the nitrogen-containing ashless friction modifier, at least one selected from the group consisting of amino acid compounds, amine compounds, urea compounds, fatty acid ester compounds, and derivatives thereof, having an alkyl group, alkenyl group, or acyl group having 12 to 30 carbon atoms, is preferred.

[0060] Suitable amino acid compounds for ashless friction modifiers containing nitrogen include the compounds shown in formula (B) below.

[0061] [ka]

[0062] Here, in equation (B) R 10 R is an alkyl group, alkenyl group, or acyl group having 12 to 30 carbon atoms. 11 R is an alkyl group or hydrogen having 1 to 4 carbon atoms. 12 R is hydrogen or an alkyl group having 1 to 10 carbon atoms. This alkyl group may include a linear, branched, or cyclic structure, the carbon atoms may be substituted with heteroatoms, and may be modified with functional groups such as hydroxyl groups, carboxyl groups, or amino groups.13 n is an alkyl group having 1 to 4 carbon atoms or a hydrogen atom, n is 0 or 1, and Y is a functional group having an active hydrogen atom, a hydrocarbon having said functional group, a metal salt or ethanolamine salt of said functional group, or a methoxy group. In formula (B), a hydroxyl group or an amino group is preferred as the functional group having an active hydrogen atom for Y.

[0063] Furthermore, as such ashless friction modifiers, R is used in terms of improving the persistence of the friction characteristic effect. 10 This is an acyl group (oleoyl group) with 18 carbon atoms, R 11 is a methyl group, R 12 Oleoyl sarcosinic acid is preferred, where is hydrogen, Y is a hydroxyl group, and n is 0.

[0064] Furthermore, suitable amine compounds as ashless friction modifiers containing nitrogen include the compounds shown in the following formula (C).

[0065] R 20 -(NR 21 )-R 22 (C) (R 20 R is an alkyl group, alkenyl group, or acyl group having 12 to 30 carbon atoms. 21 , R 22 (Each of these is independently a hydrogen atom, an alkyl group, an alkenyl group, an acyl group, or a hydroxyalkyl group.) Examples of amine compounds represented by formula (C) include oleylamine and stearylamine, with oleylamine being preferred. Furthermore, 2,2'-(octadecane-1-ylimino)diethanol can also be cited as a suitable amine compound represented by formula (C).

[0066] Furthermore, as a urea compound suitable as an ashless friction modifier containing nitrogen, a compound having the structure represented by the following formula (D) is preferred.

[0067] R 30 -NH-CO-NH2(D) (R 30(These are alkyl groups, alkenyl groups, or acyl groups having 12 to 30 carbon atoms.) Such urea compounds are preferably aliphatic urea compounds, and more preferably octadecenylurea.

[0068] The fatty acid ester compounds suitable as ashless friction modifiers containing nitrogen are not particularly limited, as they are compounds formed by ester bonding between the carboxyl group of a fatty acid and an alcohol. However, suitable examples include esters of linear or branched fatty acids with aliphatic monohydric alcohols or aliphatic polyhydric alcohols. The fatty acid may be a saturated fatty acid or an unsaturated fatty acid. The number of carbon atoms in these fatty acid ester compounds may be, for example, 7 to 31. Preferably, the fatty acid ester compound is an ester of a fatty acid and an aliphatic polyhydric alcohol, more preferably an ester of a linear fatty acid and an aliphatic polyhydric alcohol, and even more preferably an ester of a linear unsaturated fatty acid and an aliphatic polyhydric alcohol. These aliphatic polyhydric alcohol esters may be complete esters or partial esters, and are preferably partial esters. Glycerin monooleate is a preferred ester of these aliphatic polyhydric alcohols.

[0069] With respect to the C12-C30 alkyl, alkenyl, or acyl groups of the aforementioned compounds suitable as ashless friction modifiers containing nitrogen, the number of carbon atoms in these groups is preferably 14-24, more preferably 16-20, and even more preferably 18. The most preferred C12-C30 alkyl, alkenyl, or acyl groups are octadecyl, 9-octadecenyl, or oleoyl groups. The alkyl, alkenyl, or acyl groups may be linear or branched, but linear is preferred.

[0070] Furthermore, suitable ashless friction modifiers include oleoyl sarcosinic acid, oleylpropanediamine, oleic acid, oleylamine, glycerol monooleate, oleyl diethanolamine, N,N-diethanololeamide, benzotriazole derivatives, and sulfurized olefins. Among these, oleoyl sarcosinic acid, oleylpropanediamine, oleic acid, oleylamine, glycerol monooleate, oleyl diethanolamine, N,N-diethanololeamide, benzotriazole derivatives, and sulfurized olefins are more preferred, oleoyl sarcosinic acid, oleylpropanediamine, oleic acid, and N,N-diethanololeamide are even more preferred, and oleoyl sarcosinic acid is particularly preferred.

[0071] When the lubricating oil composition for internal combustion engines of the present invention contains an ashless friction modifier, the content of the ashless friction modifier is preferably 0.001 mass% to 5.0 mass%, more preferably 0.01 mass% to 1.0 mass%, and even more preferably 0.1 mass% to 0.5 mass%, based on the total amount of the composition.

[0072] When the lubricating oil composition for internal combustion engines of the present invention contains an ashless friction modifier, and the ashless friction modifier is an ashless friction modifier containing nitrogen, the nitrogen content derived from the ashless friction modifier is preferably 10 masssppm or more and 500 masssppm or less (more preferably 50 masssppm or more and 400 masssppm or less, and even more preferably 100 masssppm or more and 300 masssppm or less). By setting the amount of nitrogen derived from the ashless friction modifier to 10 masssppm or more, it is possible to reduce the friction coefficient.

[0073] Furthermore, the lubricating oil composition for internal combustion engines of the present invention preferably contains an antioxidant. Known antioxidants such as phenolic antioxidants and amine-based ashless antioxidants can be used as such antioxidants. Such antioxidants may be used individually or in combination of two or more in any proportion.

[0074] Examples of such phenolic antioxidants include 2,6-di-t-butyl-4-methylphenol, 4,4'-methylenebis(2,6-di-t-butylphenol), and octyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate.

[0075] Furthermore, amine-based ashless antioxidants used in the field of lubricating oil compositions for internal combustion engines can be used. As amine-based ashless antioxidants, alkyldiphenylamines having the following general formula (E) structure are preferred.

[0076] [ka]

[0077] In formula (E), R 60 and R 61 R may be the same or different, and each represents a hydrogen atom or an alkyl group having 1 to 16 carbon atoms. 60 , R 61 They don't all turn into hydrogen at the same time. 60 and R 61 Examples of alkyl groups represented by include methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, and hexadecyl groups (these alkyl groups may be linear or branched), but among these, the nonyl group, which is a linear alkyl group with 9 carbon atoms, is preferred.

[0078] When the lubricating oil composition for internal combustion engines of the present invention contains an antioxidant, the antioxidant content is preferably 0.1 mass% to 5.0 mass% (more preferably 1.5 mass% to 3.0 mass%) based on the total amount of the composition.

[0079] Furthermore, the lubricating oil composition for internal combustion engines of the present invention preferably contains an anti-wear agent. The anti-wear agent is not particularly limited, and known compounds used as anti-wear agents can be used in the lubricating oil composition. Examples of anti-wear agents include phosphorus-based and sulfur-phosphorus-based anti-wear agents. Examples of such anti-wear agents include phosphite esters, thiophosphite esters, dithiophosphite esters, trithiophosphite esters, phosphate esters, thiophosphate esters, dithiophosphate esters, trithiophosphate esters, amine salts thereof, metal salts thereof, and derivatives thereof. Such anti-wear agents may be used individually or in combination of two or more types.

[0080] Furthermore, zinc dialkyldithiophosphate (ZnDTP) or zinc dialkylphosphate is preferred as the anti-wear agent. The compound shown in the following formula (F) is preferred as such zinc dialkyldithiophosphate.

[0081] [ka]

[0082] In the above general formula (F), R 80 ~R 83 Each of these is independently a linear or branched alkyl group having 1 to 24 carbon atoms. This alkyl group may be primary, secondary, or tertiary. As the zinc dialkyldithiophosphate, zinc dithiophosphate having a primary alkyl group (primary ZnDTP) or zinc dithiophosphate containing a secondary alkyl group (secondary ZnDTP) is preferred, and in particular, a zinc dithiophosphate mainly composed of a secondary alkyl group is preferred in order to enhance wear resistance. Furthermore, when primary ZnDTP and secondary ZnDTP are used in combination, their mass ratio ([primary ZnDTP]:[secondary ZnDTP]) is preferably 80:20 to 10:90, and more preferably 30:70 to 20:80.

[0083] When the lubricating oil composition for internal combustion engines of the present invention contains an anti-wear agent, the content of the anti-wear agent is preferably 0.1 mass% to 1.6 mass% (more preferably 0.9 mass% to 1.5 mass%) based on the total amount of the composition. Furthermore, when the lubricating oil composition for internal combustion engines of the present invention contains an anti-wear agent comprising a phosphorus-containing compound, the amount of phosphorus derived from the anti-wear agent is preferably 10 masspm to 900 masspm (more preferably 600 masspm to 800 masspm, and even more preferably 750 masspm to 785 masspm) based on the total amount of the composition.

[0084] Furthermore, the lubricating oil composition for internal combustion engines of the present invention preferably contains a dispersant. Such a dispersant is not particularly limited, and known ashless dispersants (see, for example, Japanese Patent Publication No. 2022-158121, Japanese Patent Publication No. 2003-155492, Japanese Patent Publication No. 2020-76004, International Publication No. 2013 / 147162, etc.) can be used as appropriate, for example succinimide and its derivatives, or benzylamine. In addition, such succinimide may be either boron-free succinimide or boron-containing succinimide, but boron-free succinimide is preferred. By using boron-free succinimide, it is possible to prevent an increase in sulfated ash content due to an increase in the amount of boron. Boron-free succinimide refers to succinimide in which some or all of the amino groups and / or imino groups have not been neutralized or amidated by boric acid, etc. For example, it is succinimide in which the boron content is 0.1 mass% or less, based on succinimide. Such ashless dispersants may be used individually or in combination of two or more in any proportion.

[0085] When the lubricating oil composition for internal combustion engines of the present invention contains a dispersant, the content of the dispersant is preferably 2.0 mass% to 7.0 mass% (more preferably 2.8 mass% to 3.6 mass%) based on the total amount of the composition. When the lubricating oil composition for internal combustion engines of the present invention contains a dispersant and the dispersant is succinimide or a derivative thereof, the amount of nitrogen derived from the dispersant is preferably 350 masspm to 2000 masspm (more preferably 370 masspm to 980 masspm, and even more preferably 400 masspm to 600 masspm) based on the total amount of the lubricating oil composition. By keeping the amount of nitrogen derived from succinimide or a derivative within the above range, low sulfated ash content and cleanliness can be ensured.

[0086] Furthermore, the lubricating oil composition for internal combustion engines of the present invention may contain a pour point depressant. While known pour point depressants can be used as appropriate and are not particularly limited, polymethacrylate (PMA) and ethylene-vinyl acetate copolymer (EVA) are preferred, for example. Furthermore, from the viewpoint of pour point depressant effect and shear stability, polymers such as PMA and EVA with a weight-average molecular weight of 10,000 to 200,000 are preferred. One pour point depressant may be used alone, or two or more may be used in combination. When a pour point depressant is used, its content is preferably 0.01 to 1.0 mass% (more preferably 0.03 to 0.6 mass%) based on the total amount of the lubricating oil composition.

[0087] Furthermore, the lubricating oil composition for internal combustion engines of the present invention may contain an anti-emulsifier. Such an anti-emulsifier may be a known anti-emulsifier, such as a polyalkylene glycol-based nonionic surfactant. The anti-emulsifier may be used alone or in combination of two or more. When the lubricating oil composition utilizes an anti-emulsifier, its content is preferably 0.005 to 5.0 mass% based on the total amount of the composition.

[0088] Furthermore, the lubricating oil composition for internal combustion engines of the present invention may also contain a metal deactivator. Such a metal deactivator is not particularly limited, but examples include imidazoline, pyrimidine derivatives, alkylthiadiazole, mercaptobenzothiazole, benzotriazole or its derivatives, tolyltriazole or its derivatives, 1,3,4-thiadiazole polysulfide, 1,3,4-thiadiazolyl-2,5-bisdialkyldithiocarbamate, 2-(alkyldithio)benzimidazole, β-(o-carboxybenzylthio)propionnitrile, and the like. The metal deactivator may be used alone or in combination of two or more. When a metal deactivator is used, its content is preferably 0.01 to 0.5 mass% (more preferably 0.02 to 0.3 mass%) based on the total amount of the composition.

[0089] Furthermore, the lubricating oil composition for internal combustion engines of the present invention may contain an antifoaming agent. Examples of such antifoaming agents include known antifoaming agents such as silicones, fluorosilicones, and fluoroalkyl ethers. When an antifoaming agent is used, its content is preferably 0 to 0.5 mass% (more preferably 0 to 0.1 mass%). While the lower limit of the content is not particularly limited, in one embodiment it may be 0.0001 mass% or more.

[0090] In the lubricating oil composition for internal combustion engines of the present invention, the contents of calcium, magnesium, sulfur, boron and nitrogen based on the total amount of the composition are each preferably within the numerical range described below. That is, from the viewpoint of achieving both the prevention of pre-ignition occurring in a low-rotation high-load region and the maintenance of detergency, the calcium content is preferably 10 massppm or more and 1800 massppm or less, more preferably 1000 massppm or more and 1540 massppm or less, based on the total amount of the composition. In addition, from the viewpoint of maintaining detergency and friction reduction performance, the magnesium content is preferably 10 massppm or more and 1600 massppm or less, more preferably 200 massppm or more and 501 massppm or less, based on the total amount of the composition. From the viewpoint of maintaining detergency and wear resistance performance, the sulfur content is preferably 100 massppm or more and 4500 massppm or less, more preferably 800 massppm or more and 2600 massppm or less, based on the total amount of the composition. From the viewpoint of maintaining fuel-saving performance, the boron content is preferably 0 massppm or more and 900 massppm or less, more preferably 0 massppm or more and 600 massppm or less, based on the total amount of the composition. The nitrogen content is preferably 800 massppm or more, more preferably 900 massppm or more and 1650 massppm or less, based on the total amount of the composition. The contents of calcium, magnesium, sulfur and boron are values measured by inductively coupled plasma optical emission spectrometry (intensity ratio method (internal standard method)) in accordance with JIS K0116, and the nitrogen content (massppm) is a value measured in accordance with JIS K2609.

[0091] The lubricating oil composition for internal combustion engines of the present invention has a kinematic viscosity at 100°C of 4.5 mm 2 / s or more and 9.3 mm 2 / s or less (more preferably 4.8 mm 2 / s or more and 7.8 mm 2 / s or less) is preferred. In addition, the lubricating oil composition for internal combustion engines of the present invention has a kinematic viscosity at 40°C of 26.0 mm 2 / s or less (more preferably 16.0 mm 2 / s or more and 23.0 mm2 / s or less, more preferably 19.0 mm 2 / s or more 22.0mm 2 A viscosity of 0.5 / s or less is preferred. By setting the kinematic viscosity of the lubricating oil composition to be below the upper limit, excellent fuel efficiency can be obtained. Furthermore, by setting the kinematic viscosity of the lubricating oil composition to be above the lower limit, excellent oil film formation at the lubrication points can be achieved, and evaporation loss of the lubricating oil composition can be further reduced.

[0092] The lubricating oil composition for internal combustion engines of the present invention preferably has a viscosity index of 120 to 450 (more preferably 138 to 380). A viscosity index of the lubricating oil composition above the lower limit improves fuel efficiency. Furthermore, a viscosity index of the lubricating oil composition below the upper limit improves cleanliness. In this specification, "viscosity index" refers to values ​​measured in accordance with JIS K 2283-1993.

[0093] Furthermore, the lubricating oil composition for internal combustion engines of the present invention preferably has a CCS viscosity of 3500 mPa·s or less at -35°C (more preferably 2800 mPa·s or less, and even more preferably 2000 mPa·s or less). If the CCS viscosity at -35°C exceeds the above upper limit, the viscous resistance becomes excessive during operation of the internal combustion engine in low-temperature environments below room temperature, which tends to impair fuel efficiency. Furthermore, the lubricating oil composition for internal combustion engines of the present invention preferably has a CCS viscosity of 7000 mPa·s or less at -40°C (more preferably 6200 mPa·s or less, even more preferably 5700 mPa·s or less, and most preferably 4000 mPa·s or less). When the CCS viscosity at -40°C exceeds the aforementioned upper limit, losses due to viscous resistance in low-temperature environments below room temperature tend to increase, and the change in viscosity with respect to temperature in the low-temperature range becomes excessive. This tends to impair stable operation by causing excessive changes in the oil film and fluid delivery state as the oil temperature rises with the operation of the internal combustion engine. For the CCS viscosity at -35°C, the value measured at a test temperature of -35°C in accordance with ASTM D5293 is adopted, and for the CCS viscosity at -40°C, the value measured using the same method as the measurement method based on ASTM D5293 is adopted, except that the test temperature is changed to -40°C.

[0094] The lubricating oil composition for internal combustion engines of the present invention preferably has an HTHS viscosity at 150°C of 1.7 mPa·s or more and 2.8 mPa·s or less (more preferably 2.3 mPa·s or more and 2.5 mPa·s or less). By setting the HTHS viscosity at 150°C to below the upper limit, good fuel efficiency can be obtained. Furthermore, by setting the HTHS viscosity at 150°C to above the lower limit, good lubricity can be obtained.

[0095] The lubricating oil composition for internal combustion engines of the present invention preferably has an HTHS viscosity at 100°C of 3.0 mPa·s or more and 5.0 mPa·s or less (more preferably 3.6 mPa·s or more and 4.7 mPa·s or less). Furthermore, the lubricating oil composition for internal combustion engines of the present invention preferably has an HTHS viscosity at 80°C of 4.6 mPa·s or more and 6.7 mPa·s or less (more preferably 5.0 mPa·s or more and 6.4 mPa·s or less). Note that the HTHS viscosity at 150°C or 100°C represents the high-temperature high-shear viscosity at each temperature (150°C or 100°C) as specified in ASTM D 4683, and the HTHS viscosity at 80°C represents the high-temperature high-shear viscosity measured using the same method as the measurement method specified in ASTM D 4683, except that the test temperature was changed to 80°C.

[0096] Furthermore, the lubricating oil composition for internal combustion engines of the present invention is preferably classified as one of the following viscosity grades (hereinafter simply referred to as "SAE viscosity grades") in the J300 standard established by the Society of Automotive Engineers (SAE): 0W-8, 0W-12, 0W-16, and 0W-20, and is particularly preferably classified as one of 0W-16 and 0W-20.

[0097] The lubricating oil composition for internal combustion engines of the present invention preferably has a sulfated ash content of 1.00 mass% or less (more preferably 0.90 mass% or less). Here, "sulfated ash content" refers to sulfated ash content measured in accordance with ASTM D874. In lubricating oil compositions for internal combustion engines, the sulfated ash content increases as the amount of metal increases, and a higher sulfated ash content tends to shorten the filter life. From this viewpoint, it is desirable to keep the sulfated ash content below the above upper limit.

[0098] The lubricating oil composition for internal combustion engines of the present invention preferably has an evaporation loss (NOACK (250°C, 1 hour) evaporation loss) measured by performing a NOACK evaporation test in accordance with ASTM D5800 at 250°C for 1 hour, which is 10.0 to 30.0 mass% (more preferably 12.0 to 30.0 mass%, even more preferably 16.0 to 30.0 mass%, and particularly preferably 21.0 to 29.5 mass%). Setting the NOACK (250°C, 1 hour) evaporation loss below the upper limit tends to yield an even higher effect in terms of low evaporation, while setting it above the lower limit tends to yield an even higher effect in terms of improving fuel efficiency.

[0099] Furthermore, the internal combustion engine lubricant composition of the present invention is subjected to a NOACK evaporation test at a temperature of 150°C based on the test method specified in ASTM D5800. The test is stopped every 4 hours, a cooling process is performed as specified in the test method, the mass is checked, and the test is restarted. This is done three times at 150°C for 4 hours each time. The evaporation loss (mass%) at the third NOACK evaporation test (after 12 hours), where the total test time is 12 hours, and the evaporation loss (mass%) at the first NOACK evaporation test (after 4 hours), where the test time is 4 hours, are used to determine the change in NOACK evaporation loss per unit time (slope) from 4 hours to 12 hours of testing. Preferably, this change is 0.45 mass% / h or less (more preferably 0.35 mass% / h or less). By keeping the change in NOACK evaporation loss per unit time below the above upper limit, it is possible to further improve the level of evaporation reduction.

[0100] The lubricating oil composition for internal combustion engines according to the present invention is more preferably characterized in that the content of components with a boiling point of 330°C or less is 4.6 mass% or less (more preferably 2.9 mass% or less) on a basis of the total amount of the composition. By keeping the content of such components with a boiling point of 330°C or less below the above upper limit, evaporation loss during use can be further reduced, and an even higher effect in terms of low evaporation can be obtained. The content of such components with a boiling point of 330°C or less can be determined by performing the "Gas Chromatography Distillation Test (A)" on the lubricating oil composition and calculating the content ratio of components with a boiling point of 330°C or less relative to the total amount of lubricating oil base oil from the gas chromatogram obtained.

[0101] The lubricating oil composition for internal combustion engines according to the present invention is more preferably characterized in that the content of components with a boiling point of 310°C or less is 3.2 mass% or less (more preferably 2.0 mass% or less) on a basis of the total amount of the composition. By keeping the content of such components with a boiling point of 310°C or less below the above upper limit, evaporation loss during use can be further reduced, and an even higher effect in terms of low evaporation can be obtained. The content of such components with a boiling point of 310°C or less can be determined by performing the "Gas Chromatography Distillation Test (A)" on the lubricating oil composition and calculating the content ratio of components with a boiling point of 310°C or less relative to the total amount of lubricating oil base oil from the gas chromatogram obtained.

[0102] Furthermore, the lubricating oil composition for internal combustion engines of the present invention can be used in devices equipped with an internal combustion engine, and is not particularly limited, but is particularly suitable as a lubricating oil composition for automobile engines equipped with a GPF (gasoline particulate filter), and for hybrid automobiles equipped with an internal combustion engine and an electric motor.

[0103] Furthermore, the method for producing the lubricating oil composition for internal combustion engines of the present invention is not particularly limited, and it may be prepared by appropriately selecting and mixing each component to be included so that the lubricating oil composition for internal combustion engines of the present invention can be obtained (so that the above conditions are met). [Examples]

[0104] The present invention will be described more specifically below based on examples and comparative examples, but the present invention is not limited to the following examples.

[0105] (Regarding the ingredients used in each example, etc.) First, Table 1 shows the abbreviations, types, and characteristics of the base oil components used in each example, and Table 2 shows the abbreviations, types, and characteristics of the additives used in each example. In the examples described below, each component will be expressed using the abbreviations listed in Tables 1 and 2, as appropriate. Furthermore, the "Content of components with a boiling point below 330°C" for the base oil components shown in Table 1 indicates the content of components with a boiling point below 330°C in that base oil, determined by a test similar to the "Gas Chromatography Distillation Test (A)" described above. In addition, the "Kinematic viscosity at 40°C" and "Kinematic viscosity at 100°C" shown in Table 1 are values ​​measured in accordance with ASTM D-445. Furthermore, the "NOACK (250°C, 1 hour) evaporation loss" shown in Table 1 indicates the evaporation loss of each base oil determined by a NOACK evaporation test under conditions of 250°C and 1 hour, in accordance with ASTM D5800. Here, since the NOACK (250°C, 1 hour) evaporation loss exceeds 60 mass%, it is not possible to measure it directly. Therefore, three or more samples were prepared, each consisting of a mixture in which the base oil in question was contained in different ratios with other base oils whose NOACK (250°C, 1 hour) evaporation loss is known. The NOACK (250°C, 1 hour) evaporation loss of each sample was determined, and an estimated value was obtained by approximating a straight line from the measured values ​​and using that value. Note that base oil components (3) and (7) to (10) shown in Table 1 consist of base oils other than ester base oils (consisting of mineral oil base oils) and satisfy all of the aforementioned conditions (I) to (IV).

[0106] [Table 1]

[0107] [Table 2]

[0108] (Examples 1-40 and Comparative Examples 1-11) Lubricant compositions for Examples 1-40 and Comparative Examples 1-11 were prepared using the aforementioned components to achieve the compositions shown in Tables 3-7. In Tables 3-7, blank spaces in the "Base Oil Component Content in Lubricant Base Oil" and "Additive Content in Lubricant Composition" columns indicate that the component was not used. Furthermore, in Tables 3-7, for the "Base Oil Component Content in Lubricant Base Oil," "Characteristics of Lubricant Base Oil," and "Additive Content in Lubricant Composition" columns, "mass%" represents the mass-based content (mass%) relative to the total amount of lubricant base oil, and "inmass%" represents the mass-based content (mass%) relative to the total amount of lubricant composition. The numerical values ​​(in mass%) for viscosity index improvers (PMA-based VI(1)-(5) and OCP-based VI) in Tables 3-7 represent the total composition-based content (viscosity index improver content converted to resin content). Furthermore, Tables 3-7 also show the content (mass ppm) of each element (Ca, Mg, Mo, P, Zn, S, and B) in the composition, measured by inductively coupled plasma atomic emission spectrometry (intensity ratio method (internal standard method)) in accordance with JIS K0116, and the nitrogen content (mass ppm) measured in accordance with JIS K2609.

[0109] [Table 3]

[0110] [Table 4]

[0111] [Table 5]

[0112] [Table 6]

[0113] [Table 7]

[0114] [Evaluation of the properties of the lubricating oil compositions obtained in each example] <Gas chromatographic distillation test> For the lubricating oil compositions obtained in each example, a test similar to the "Gas Chromatography Distillation Test (A)" described above was performed to obtain a gas chromatogram. From these gas chromatograms, the content of components with a boiling point of less than 240°C and the content of components with a boiling point in the range of {(i-1)×10}°C or higher and less than (i×10)°C (where i is an integer from 25 to 60, and measurements were taken for all values) were determined (unit: mass%: mass ratio based on the total amount of the composition). In addition, from the gas chromatograms, the content (total amount) of components with a boiling point of 310°C or lower and the content (total amount) of components with a boiling point of 330°C or lower in the lubricating oil composition were determined. Tables 8-11 show the content (in mass%) of components with a boiling point between {(i-1)×10}°C and (i×10)°C (where i is an integer between 25 and 60) as a result of the gas chromatography distillation test (A). Tables 12-15 show the total content of components with a boiling point of 310°C or lower and the total content of components with a boiling point of 330°C or lower. However, any component with a measured content of less than 0.01 mass% is considered to have a content of 0, taking into account the test accuracy (test error), and is indicated as 0.00 in Tables 8-11. In all of the lubricating oil compositions measured, the content of components with a boiling point below 240°C was 0.00 mass%.

[0115] <Measurement of kinematic viscosity and viscosity index> The kinematic viscosity at 40°C and 100°C was measured for the lubricating oil compositions obtained in each example, in accordance with ASTM D-445. Furthermore, the viscosity index was determined for the lubricating oil compositions obtained in each example, in accordance with JIS K 2283-1993. The results are shown in Tables 12-15. Note that the kinematic viscosity at 40°C was 26.0 mm². 2 If the value is less than or equal to / s, it can be evaluated that the kinematic viscosity in the low-temperature range is sufficiently low.

[0116] <Measurement of high-temperature high-shear viscosity (HTHS viscosity)> The high-temperature high-shear viscosity (HTHS viscosity) of the lubricating oil compositions obtained in each example was measured at 150°C, 100°C, and 80°C. The HTHS viscosity at 150°C or 100°C represents the high-temperature high-shear viscosity at each temperature (150°C or 100°C) as specified in ASTM D 4683, while the HTHS viscosity at 80°C represents the high-temperature high-shear viscosity measured using the same method as specified in ASTM D 4683, except that the test temperature was changed to 80°C. The results are shown in Tables 12 to 15.

[0117] <Method for measuring low-temperature cranking (CCS) viscosity> For the lubricating oil compositions obtained in each example, the CCS viscosity at -35°C was measured in accordance with ASTM D5293. The CCS viscosity at -40°C was also measured by employing the same method as the CCS viscosity measurement method in accordance with ASTM D5293, except that the temperature condition was changed to -40°C. Using these measurement results, the change in CCS viscosity with respect to the temperature change from -35°C to -40°C (the change in CCS viscosity per 1°C (the increase for each 1°C decrease)) and the ratio of CCS viscosity ([CCS viscosity at -40°C] / [CCS viscosity at -35°C]) were also determined. The obtained results are shown in Tables 12 to 15.

[0118] <Measurement of acid value, base value (hydrochloric acid method), and base value (perchloric acid method)> For the lubricating oil compositions obtained in each of the examples and other test groups, the acid value, base number (hydrochloric acid method) and base number (perchloric acid method) were measured respectively in accordance with JIS K2501:2003. The obtained results are shown in Tables 12 to 15.

[0119] <Measurement of USV Viscosity> For the lubricating oil compositions obtained in each of the examples and other test groups, at temperatures of 40°C and 60°C respectively, a USV viscometer manufactured by PCS Instruments was used to conduct measurement at a shear rate of 1×10 6 / s to measure the USV viscosity. The obtained results are shown in Tables 12 to 15.

[0120] <Measurement of Sulfated Ash Content> For the lubricating oil compositions obtained in each of the examples and other test groups, the sulfated ash content (mass%) was measured in accordance with JIS K2272. The obtained results are shown in Tables 12 to 15.

[0121] <Measurement of NOACK Evaporation Loss> For the lubricating oil compositions obtained in each example, etc., the NOACK evaporation loss was determined as follows. Specifically, first, for each composition sample, a test identical to the NOACK evaporation test specified in ASTM D5800 was performed three times each, except that the temperature condition was changed to 150°C and the test duration was changed to 4 hours. Such three tests were conducted by a method in which the test was temporarily stopped each time 4 hours of test time elapsed, a cooling step specified in the test method (the NOACK evaporation test specified in ASTM D5800) was performed, the mass was then checked, and the test was resumed. In this way, the NOACK evaporation test employing conditions of 150°C and 4 hours was intermittently performed three times on each sample (by a method in which a cooling step is performed once every 4 hours, the mass is measured, and then the test is resumed). Then, the NOACK evaporation loss (mass%) (150°C, 12 hours) obtained in the third NOACK evaporation test (after 12 hours) with a total test time of 12 hours, and the NOACK evaporation loss (mass%) (150°C, 4 hours) obtained in the first NOACK evaporation test (after 4 hours) with a test time of 4 hours were each determined, and the change in NOACK evaporation loss per unit time between 4 hours and 12 hours of test time (hereinafter referred to as "NOACK slope at 150°C" in some cases; unit: mass% / h) was calculated. When the NOACK slope at 150°C is 0.45 mass% / h or less, it can be evaluated as a low-evaporation product without sudden occurrence of evaporation loss. The obtained results are shown in Tables 12 to 15. Separately from the above test, the lubricating oil compositions obtained in each example, etc., were subjected to the NOACK evaporation test specified in ASTM D5800 under conditions of 250°C and 1 hour, and the evaporation loss (mass%) of the lubricating oil composition was determined. The obtained results are shown in Tables 12 to 15.

[0122] <Characteristic Evaluation of Oxidatively Degraded Oil by ISOT Test> For the lubricating oil compositions obtained in each example, first, unused samples (new oil) were oxidized using the ISOT method (Indiana Stirring Oxidation Test) specified in JIS K2514-1 under conditions of a temperature of 165°C and a test time of 168 hours to obtain oxidized degraded oil. Next, using the oxidized degraded oil treated by the ISOT method, the kinematic viscosity at 40°C, acid value, base value (hydrochloric acid method), and base value (perchloric acid method) were measured using the same methods as described above. The results obtained, including the percentage increase in the kinematic viscosity at 40°C after ISOT relative to the kinematic viscosity of new oil, the acid value after ISOT, the base value after ISOT (hydrochloric acid method), the base value after ISOT (perchloric acid method), and the increase in the acid value after ISOT, are shown in Tables 12 to 15, respectively.

[0123] <Evaluation by hot tube test (evaluation of high-temperature cleanliness)> For each lubricating oil composition obtained in the examples, a hot tube test (HTT) was performed in accordance with JPI-5S-55-99, using a sample volume of 5 mL, a test temperature of 280°C, and a test time of 16 hours to evaluate its high-temperature cleanliness. The HTT score ranges from a maximum of 10 points to a minimum of 0 points, with higher scores indicating better high-temperature cleanliness. The results are shown in Tables 12-15.

[0124] <Measurement of friction coefficient (SRV test)> The friction coefficient was measured by performing SRV tests on the lubricating oil compositions obtained in each example as follows. First, a standard test piece conforming to ASTM D5706 [consisting of a cylinder (size: 15 mm (diameter) × 22 mm) and a disc (size: 24 mm (diameter) × 6.9 mm)] was prepared using an SRV testing machine manufactured by Optimol. Each lubricating oil composition was dropped onto the sliding surface of the test piece, and tests were conducted at 120°C and 40°C under the conditions of a load of 400 N, vibration frequency of 50 Hz, amplitude of 1.5 mm, and test time of 15 minutes. The average friction coefficient was measured from 10 minutes after the start of the test until 15 minutes after the start of the test (between 10 and 15 minutes of the test). The results obtained are shown in Tables 12 to 15.

[0125] [Table 8]

[0126] [Table 9]

[0127] [Table 10]

[0128] [Table 11]

[0129] [Table 12]

[0130] [Table 13]

[0131] [Table 14]

[0132] [Table 15]

[0133] As is clear from the compositions, experimental results and the like shown in Tables 3 to 15, the lubricating base oil has a kinematic viscosity at 100°C of 2.7 mm 2 2 2 / s or more and 4.0 mmThe lubricating oil compositions produced in Examples 1 to 40 all satisfy the following conditions: the viscosity is less than or equal to / s; the evaporation loss of the lubricating oil base oil, as determined by a NOACK evaporation test at 250°C for 1 hour, is 34.0 mass% or less; the lubricating oil base oil does not contain ester base oil as a constituent base oil component; the lubricating oil base oil contains at least one base oil component that satisfies the above conditions (I) to (IV); the lubricating oil base oil contains a total of 30 mass% or more of the base oil components that satisfy the above conditions (I) to (IV) based on the total amount of the lubricating oil base oil; and the viscosity index improver is poly(meth)acrylate. 2 The kinematic viscosity was less than / s, confirming that the kinematic viscosity in the low-temperature range is sufficiently low. Furthermore, the change in NOACK evaporation loss per unit time (NOACK slope at 150°C) from 4 hours to 12 hours of testing was 0.45 mass% / h or less in all cases, indicating a high level of suppression of evaporation loss during use and confirming a high level of low evaporation properties. The lubricating oil compositions produced in Examples 1 to 40 all had a kinematic viscosity of 4.5 mm at 100°C. 2 Since the viscosity is 1 / s or higher, and the viscosity of the lubricating oil composition in the high-temperature range also meets the level required for internal combustion engines, it has been found that according to the present invention, it is possible to achieve both low viscosity and low evaporation at low temperatures, including room temperature, while maintaining the viscosity of the lubricating oil composition above a certain value in the high-temperature range.

[0134] In contrast, the lubricating oil base has a kinematic viscosity of 2.7 mm at 100°C. 2 / s or more 4.0mm 2The lubricating oil compositions produced in Comparative Examples 1 to 11 that do not satisfy at least one of the following conditions: the lubricating oil composition is less than or equal to / s; the lubricating oil base oil has an evaporation loss of 34.0 mass% or less as determined by a NOACK evaporation test at 250°C for 1 hour; the lubricating oil base oil does not contain ester base oil as a constituent base oil component; the lubricating oil base oil contains at least one base oil component that satisfies the above conditions (I) to (IV) as a constituent component; the lubricating oil base oil contains a total of 30 mass% or more of the base oil components that satisfy the above conditions (I) to (IV) based on the total amount of the lubricating oil base oil; and the viscosity index improver is poly(meth)acrylate, have a kinematic viscosity of 26.0 mm² at 40°C. 2 The product failed to meet either or both of the following conditions: that the viscosity is less than or equal to / s, and that the NOACK slope at 150°C is less than or equal to 0.45 mass% / h. Therefore, it was confirmed that it is not possible to achieve both low evaporation and low viscosity characteristics simultaneously.

[0135] Furthermore, from the compositions and experimental results shown in Tables 3-15, it can be confirmed that the lubricating oil composition produced in Example 1 is a composition with an SAE viscosity grade of 0W-16. Comparing Examples 1-4, although the compositions differ in the amount of molybdenum-based friction modifier added, the kinematic viscosity at 40°C for all compositions is 26.0 mmHg. 2 Since the values ​​were less than / s and the NOACK slope at 150°C was 0.45 mass% / h or less in all cases, it became clear that the amount of molybdenum-based friction modifier used can be appropriately changed according to the product design without impairing evaporation or fuel efficiency. This made it possible to suitably adjust (improve) cleanliness, cleanliness retention, and intermetallic friction reduction performance according to the application.

[0136] Furthermore, the lubricating oil compositions produced in Examples 5-6 and the lubricating oil composition produced in Example 1 differ in their combination of base oil components (although the kinematic viscosity of the lubricating oil base oil at 100°C is similar), and since both achieved both low evaporation and low viscosity characteristics, it was found that by combining and using base oil components to satisfy the conditions for the internal combustion engine lubricating oil composition of the present invention, it is possible to achieve high levels of both low evaporation and low viscosity characteristics. It should be noted that the base oil component (base oil component (7) or base oil component (8)) used in Examples 5-6 that satisfies the above conditions (I)-(IV) has a smaller calculated value X obtained by formula (1) than the base oil component (9) used in Example 1. From the comparison between these examples, it can be understood that the slope of NOACK at 150°C becomes smaller due to the smaller calculated value X, and it is considered that an even greater effect in terms of low evaporation can be obtained by making the calculated value X smaller. Furthermore, comparing Example 1 with Examples 5-6, the kinematic viscosity at 40°C of the lubricating oil compositions produced in Examples 5-6 was lower, indicating that fuel efficiency can be further improved by using compositions like those employed in Examples 5-6.

[0137] In contrast, the kinematic viscosity of the lubricating oil base oil at 100°C is 2.7 mm². 2 / s or more 4.0mm 2 The lubricating oil composition produced in Comparative Example 1, which did not meet the condition of being less than or equal to / s, had a kinematic viscosity of 26.0 mm² at 40°C. 2 The viscosity exceeded / s, resulting in insufficient low viscosity characteristics and inadequate fuel efficiency. Furthermore, when considering the composition of the lubricating oil base oil used in the lubricating oil composition produced in Example 1 as a reference, the lubricating oil compositions produced in Comparative Examples 2 and 3, which included a lubricating oil base oil in which a base oil component whose calculated value X, determined by formula (1), exceeds 100, instead of using a base oil component that satisfies the above conditions (I) to (IV) in combination with base oil component (1), showed a NOACK slope value at 150°C exceeding 0.45 mass% / h, and were insufficient in terms of low evaporation.

[0138] Furthermore, the lubricating oil compositions produced in Comparative Examples 4 to 7 using base oil component (4) and / or base oil component (6), which are ester base oils, all had a kinematic viscosity of 26.0 mm at 40°C. 2 The viscosity exceeded 0.45 mass% / h, resulting in insufficient low-viscosity characteristics and thus inadequate fuel efficiency. Furthermore, the results shown in Comparative Examples 4-7 indicate that when ester base oil is used to achieve high-temperature high-shear viscosity at 100°C and 150°C equivalent to that of Example 1, the kinematic viscosity in the low-temperature range becomes high, impairing fuel efficiency. Moreover, the lubricating oil compositions produced in Comparative Examples 4 and 6-7 not only failed to exhibit sufficient low-viscosity characteristics as described above, but also exceeded 0.45 mass% / h in NOACK slope at 150°C, indicating insufficient low evaporation.

[0139] Furthermore, the lubricating oil composition produced in Example 7 had an SAE viscosity grade of 0W-8. Also, although the lubricating oil compositions produced in Examples 7-9 differed in composition from Example 1 in that the types and amounts of detergents and antioxidants were changed, the kinematic viscosity at 40°C for all compositions was 26.0 mmHg. 2 Since the values ​​were less than / s and the NOACK slope at 150°C was 0.45 mass% / h or less in all cases, it was found that it is possible to improve cleanliness and cleanliness retention by appropriately changing the type and amount of cleaning agents and antioxidants used according to the product design, without impairing evaporability or fuel efficiency.

[0140] Furthermore, the lubricating oil compositions produced in Examples 10 to 11 utilize base oil component (9) that satisfies the above conditions (I) to (IV), as well as base oil component (3) that satisfies the above conditions (I) to (IV). While Example 1 differs mainly in that the composition of the lubricating oil base oil is a combination of base oil component (1) and base oil component (9), it can be seen that in Examples 10 to 11, the kinematic viscosity of the composition at 40°C is further reduced, the viscous resistance at room temperature is further reduced, and the fuel efficiency performance is at an even higher level, due to the calculated value X of base oil component (3) being smaller than the calculated value X of base oil component (9). Furthermore, in Example 12, the composition of the lubricating oil base differs from Examples 10-11 in that it utilizes base oil component (8), which has an even smaller calculated value X than base oil component (3), and has a high concentration of base oil component (8) at 84 mass%. This further reduces the kinematic viscosity of the composition at 40°C, resulting in an even greater effect in terms of low viscosity in the low-temperature range. In addition, the lubricating oil composition produced in Example 13 has a higher content of base oil components that satisfy the above conditions (I)-(IV) compared to the lubricating oil composition produced in Example 1, but has a lower total content of base oil components that satisfy the above conditions (I)-(IV) compared to the lubricating oil compositions produced in Examples 10-12. Comparing Example 13 with Examples 1 and 10-12, it can be seen that the lubricating oil composition produced in Example 13 has a lower kinematic viscosity at 40°C than the lubricating oil composition produced in Example 1, but a higher kinematic viscosity at 40°C compared to the lubricating oil compositions produced in Examples 10-12. On the other hand, the lubricating oil composition produced in Example 13 showed a lower NOACK slope at 150°C than Examples 1, 10, and 12, demonstrating a high level of effectiveness in terms of low evaporation. From these results, it can be seen that, depending on the design and operating conditions of the product to which the lubricating oil composition is applied, it is possible to prepare and use a suitable lubricating oil base oil for each application by appropriately changing the type and composition of the base oil components used in the lubricating oil base oil so as to satisfy all of the above conditions.

[0141] Furthermore, although the lubricating oil base oil obtained by combining base oil components that satisfy the above conditions (I) to (IV) was used, the lubricating oil composition produced in Comparative Example 8, in which the NOACK (250°C, 1 hour) evaporation loss of the lubricating oil base oil exceeded 34.0 mass%, had a NOACK slope of 0.56 mass% / h at 150°C, which was not sufficient in terms of low evaporation.

[0142] Furthermore, the lubricating oil composition produced in Comparative Example 9, which does not utilize base oil components that satisfy the above conditions (I) to (IV), and in which the kinematic viscosity of the lubricating oil base oil at 100°C is 4.0 or higher, has a kinematic viscosity of 26.0 mm at 40°C. 2 The viscosity exceeded / s, resulting in insufficient low viscosity characteristics and inadequate fuel efficiency. Furthermore, in the lubricating oil composition produced in Comparative Example 10, which utilizes base oil components that satisfy the above conditions (I) to (IV), and in which the total amount of base oil components that satisfy the above conditions (I) to (IV) is 5 mass%, the kinematic viscosity at 40°C was 26.0 mm². 2 The viscosity exceeded / s, and the low viscosity characteristics were not at a sufficient level. From these results, it was found that, from the viewpoint of reducing viscosity, the content (total amount) of base oil components that satisfy the above conditions (I) to (IV) in the lubricating oil base oil needs to be 30 mass% or more, as in Example 1.

[0143] Furthermore, when comparing the lubricating oil compositions produced in Examples 15-18, although the type and amount of PMA-based viscosity index improver used were changed for each composition, the kinematic viscosity at 40°C was 26.0 mm² for all compositions. 2The viscosity was less than / s, and the NOACK slope at 150°C was 0.45 mass% / h or less in all cases. From these results, it was found that by including a PMA-based viscosity improver, it is possible to use it by appropriately changing the type, etc., according to the product design without impairing evaporability or fuel efficiency. In contrast, in Comparative Example 9, which did not use a PMA-based viscosity index improver but contained an OCP-based viscosity index improver (olefin copolymer), the HTHS viscosity at 150°C was equivalent to that of Examples 16-19 and met the standards set by SAE J300, but the kinematic viscosity of the composition at 40°C was 36.5 mm 2 The result was / s, which is insufficient in terms of fuel efficiency.

[0144] Furthermore, when comparing the lubricating oil compositions produced in Examples 19 to 28, although their compositions differ in that the type and amount of ashless friction modifier (organic FM agent) used are changed, the kinematic viscosity of all compositions at 40°C is 26.0 mm². 2 Since the values ​​were less than / s and the NOACK slope at 150°C was 0.45 mass% / h or less in all cases, it was found that it is possible to design the composition by appropriately changing the type of ashless friction modifier, etc., according to the desired friction reduction performance, without impairing evaporability or fuel efficiency.

[0145] Furthermore, in Examples 36-38, the amount of metal-based detergent, antioxidant, and dispersant used was changed, respectively, to alter the sulfated ash content. However, the lubricating oil compositions produced in Examples 36-38 all had a kinematic viscosity of 26.0 mm at 40°C. 2Since the viscosity was less than / s and the NOACK slope at 150°C was 0.45 mass% / h or less in all cases, it was found that it is possible to design compositions by appropriately changing the types and amounts of components such as metallic detergents, antioxidants, and dispersants, from the viewpoint of GPF compliance performance and friction reduction performance, without impairing evaporation performance or fuel efficiency performance. Furthermore, while Examples 39 to 40 are examples in which the kinematic viscosity of the lubricating oil base oil at 100°C is further reduced compared to Example 1, it is possible to further improve the low viscosity characteristics of the resulting compositions, and it is also possible to make the NOACK slope at 150°C of the compositions even lower, and it can be confirmed that higher performance in terms of low evaporation is also obtained.

[0146] Based on these results, in a lubricating oil composition containing a lubricating oil base and a viscosity index improver, the kinematic viscosity of the lubricating oil base at 100°C is 2.7 mm². 2 / s or more 4.0mm 2 It can be seen that by satisfying all of the following conditions, the composition will have sufficiently high levels of low evaporation and fuel efficiency: the viscosity must be less than or equal to / s; the evaporation loss of the lubricating oil base oil, as determined by a NOACK evaporation test at 250°C for 1 hour, must be 34.0 mass% or less; the lubricating oil base oil must not contain ester base oil as a constituent base oil component; the lubricating oil base oil must contain at least one base oil component that satisfies the above conditions (I) to (IV); the lubricating oil base oil must contain a total of 30 mass% or more of the base oil components that satisfy the above conditions (I) to (IV) on a total basis of the lubricating oil base oil; and the viscosity index improver must be poly(meth)acrylate. [Industrial applicability]

[0147] As described above, the present invention makes it possible to provide a lubricating oil composition for internal combustion engines that achieves both low viscosity and low evaporation at high levels in the low-temperature range. Because such a lubricating oil composition for internal combustion engines of the present invention can achieve both low viscosity and low evaporation at high levels, it is particularly useful as a lubricating oil composition for automobile engines equipped with a GPF (gasoline particulate filter), or as a lubricating oil composition for hybrid automobiles equipped with an internal combustion engine and an electric motor.

Claims

1. A lubricating oil composition for internal combustion engines, comprising a lubricating oil base oil and a viscosity index improver, The aforementioned lubricating oil base oil has a kinematic viscosity of 2.7 mm at 100°C. ２ / s or more 4.0mm ２ Those less than or equal to / s, The aforementioned lubricating oil base oil is one in which the evaporation loss of the lubricating oil base oil, as determined by a NOACK evaporation test under the conditions of 250°C for 1 hour, is 34.0 mass% or less. The aforementioned lubricating oil base oil does not contain ester base oil as a constituent base oil component. The aforementioned lubricating oil base oil has the following constituent components: (I) to (IV): [Condition (I)] Kinematic viscosity at 100°C is 1.8 mm ２ / s or more 3.9mm ２ It must be less than or equal to / s. [Condition (II)] Kinematic viscosity at 40°C is 5.5 mm ２ / s or more 20.0mm ２ It must be less than or equal to / s. [Condition (III)] The evaporation loss of base oil components, as determined by a NOACK evaporation test at 250°C for 1 hour, must be 50.0 mass% or less. [Condition (IV)] The following formula (1): X=Y×4.6+Z (1) (In the formula, Y represents the kinematic viscosity of the base oil component at 40°C, and Z represents the evaporation loss of the base oil component determined by a NOACK evaporation test under conditions of 250°C for 1 hour.) The calculated value X obtained by this method must be 100 or less. It contains at least one base oil component that satisfies the following conditions: The lubricating oil base oil contains a total of 30 mass% or more of base oil components that satisfy the above conditions (I) to (IV) on a basis of the total amount of the lubricating oil base oil, and A lubricating oil composition for internal combustion engines, characterized in that the viscosity index improver is poly(meth)acrylate.

2. The lubricating oil composition for internal combustion engines according to claim 1, characterized in that the lubricating oil base oil contains a total of 50 mass% or more of base oil components that satisfy the above conditions (I) to (IV) based on the total amount of the lubricating oil base oil.

3. The lubricating oil composition for internal combustion engines according to claim 1, characterized in that the evaporation loss of the lubricating oil base oil, as determined by a NOACK evaporation test under the conditions of 250°C for 1 hour, is 31.0 mass% or less.

4. The lubricating oil composition for internal combustion engines according to claim 1, characterized in that the lubricating oil base oil contains at least one mineral oil-based base oil as a base oil component constituting the lubricating oil base oil.

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