Lubricating oil composition for internal combustion engines

Abstract

To provide a lubricant composition for an internal combustion engine that exhibits both of high fuel-saving performance and LSPI-reducing effect.SOLUTION: Provided is a lubricant composition for an internal combustion engine, comprising: (A) a lubricant base oil which contains one or more mineral-oil-based base oils and which has a kinematic viscosity of 2.5-4.0 mm2 / s at 100°C; and (B) magnesium salicylate of 0.1-10 mass% based on the total amount of the composition, where the HTHS viscosity is 1.6-2.5 mPa s at 150°C.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a lubricating oil composition for an internal combustion engine, and more particularly to a lubricating oil composition for an internal combustion engine of a passenger vehicle. [Background technology]

[0002] In recent years, various demands have been placed on automotive internal combustion engines, such as smaller size, higher output, improved fuel economy, and compliance with exhaust gas regulations. In particular, there has been a trend toward downsizing and turbocharging of automotive internal combustion engines in order to improve the fuel economy of these engines.

[0003] Downsizing turbo engines have a higher compression ratio than normal engines, and the increased frequency of abnormal combustion (LSPI: Low Speed ​​Pre-Ignition) at low engine speeds is an issue (Non-Patent Document 1). It is believed that calcium-based detergents in lubricating oils for internal combustion engines cause LSPI. For this reason, lubricating oils for internal combustion engines in which some of the metal-based detergents have been replaced with magnesium-based detergents have been developed to maintain the cleanliness and neutrality of the lubricating oils for internal combustion engines (Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2017-105886 A [Patent Document 2] JP 2016-196667 A

[0005] [Non-Patent Document 1] Fujimoto, K.; Yamashita, M.; Hirano, S.; Kato, K. et al., "Engine Oil Development for Preventing Pre-Ignition in Turbocharged Gasoline Engine", SAE Int. J. Fuels Lubr. 7(3):2014, doi:10.4271 / 2014-01-2785. Summary of the Invention [Problem to be solved by the invention]

[0006] On the other hand, even when the amount of magnesium-based detergent among metal-based detergents is increased, further improvement in fuel economy is required. The lubricating oils for internal combustion engines described in Patent Documents 1 and 2 sometimes fail to provide good fuel economy performance and a reduction effect in LSPI. [Means for solving the problem]

[0007] The present inventors have conducted extensive research into a lubricating oil composition for internal combustion engines that combines fuel economy performance and LSPI reduction effects. As a result of their research, the present inventors have found that by combining a specific HTHS viscosity at 150°C in a lubricating oil for internal combustion engines with magnesium salicylate as a metal detergent, it is possible to achieve both an LSPI reduction effect and further improvement in fuel economy performance. That is, the present inventors have found that the above-mentioned problems can be solved by adopting the following configuration, and have completed the invention.

[0008] The present invention has been made based on such findings and is as follows. <1> (A) A mixture containing one or more mineral base oils and having a kinematic viscosity of 2.5 mm at 100°C. 2 / s or more 4.0mm 2 / s or less of lubricating oil base oil, and (B) Magnesium salicylate in an amount of 0.1% by mass or more and 10% by mass or less based on the total amount of the composition A lubricating oil composition for an internal combustion engine comprising: The lubricating oil composition for internal combustion engines has an HTHS viscosity at 150°C of 1.6 mPa·s or more and 2.5 mPa·s or less. <2> (B) the content of magnesium salicylate is 0.1% by mass or more and 3.0% by mass or less based on the total amount of the composition, and (C) The content of the viscosity index improver is 0.1% by mass or more and 10% by mass or less based on the total amount of the composition; <1> The lubricating oil composition for internal combustion engines according to claim 1. <3> As a friction modifier, the composition further contains (D) a molybdenum-based friction modifier in an amount of 0.01 mass% or more and 10 mass% or less based on the total amount of the composition. <1> or <2> The lubricating oil composition for internal combustion engines according to claim 1. <4> The base number of the magnesium salicylate is 350 mgKOH / g or less. <1> ~ <3> 2. The lubricating oil composition for internal combustion engines according to claim 1 . <5> The HTHS viscosity at 150°C is 1.6 mPa·s or more and 2.0 mPa·s or less. <1> ~ <4> 2. The lubricating oil composition for internal combustion engines according to claim 1 . <6> The LSPI frequency index calculated by the following formula (6) is 0 or less. <1> ~ <5> 2. The lubricating oil composition for internal combustion engines according to claim 1 . Formula (6) LSPI frequency index = 6.59 x Ca - 26.6 x P - 5.12 x Mo + 1.69 (In formula (6), Ca represents the calcium content (% by mass) in the composition, P represents the phosphorus content (% by mass) in the composition, and Mo represents the molybdenum content (% by mass) in the composition.) Effect of the Invention

[0009] According to the lubricating oil composition for internal combustion engines of the present invention, it is possible to provide a lubricating oil composition for internal combustion engines which combines good fuel economy performance and an effect of reducing LSPI. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] [A] Lubricant base oil In the lubricating oil composition of the present invention, a mineral base oil can be used as the lubricating base oil.

[0011] The mineral oil base oil used in the lubricating oil composition of the present invention may be a distillate oil obtained by distilling crude oil at atmospheric pressure. Alternatively, the distillate oil obtained by further distilling the distillate oil under reduced pressure may be refined by various refining processes to obtain a lubricating oil fraction. The refining process may be a combination of hydrorefining, solvent extraction, solvent dewaxing, hydrodewaxing, sulfuric acid washing, clay treatment, etc., as appropriate. By combining and processing these refining processes in an appropriate order, a lubricating oil base oil that can be used in the present invention may be obtained. A mixture of multiple refined oils with different properties obtained by subjecting different crude oils or distillate oils to a combination of different refining processes may also be used.

[0012] The mineral base oil used in the lubricating oil composition of the present invention is preferably one belonging to API Group III base oil. API Group III base oil is a mineral base oil having a sulfur content of 0.03 mass% or less, a saturate content of 90 mass% or more, and a viscosity index of 120 or more. Multiple types of Group III base oils may be used, or only one type may be used.

[0013] The lubricating oil composition of the present invention may contain only mineral base oil as the lubricating oil base oil, or may contain other lubricating oil base oils. Specifically, the content of the mineral base oil in the lubricating oil composition of the present invention may be, for example, 50 mass% or more, 60 mass% or more, 70 mass% or more, 80 mass% or more, 90 mass% or more, 95 mass% or more, or 99 mass% or more based on the lubricating oil base oil. Other lubricating base oils that can be used include, for example, synthetic base oils, such as polyolefins such as poly-α-olefins, polyesters, polyalkylene glycols, alkylbenzenes, alkylnaphthalenes, and GTL base oils.

[0014] The kinematic viscosity at 100°C of the lubricating base oil contained in the lubricating oil composition of the present invention is 2.5 mm 2 / s or more 4.0mm 2 The kinematic viscosity of the lubricating base oil of the present invention at 100° C. is preferably 3.0 mm 2 / s or more, preferably 3.2 mm 2 / s or more, and preferably 3.4 mm 2 The upper limit is preferably 3.9 mm / s or more. 2 / s or less, preferably 3.8 mm 2 / s or less, and more preferably 3.6 mm 2 / s or less. The specific range is 2.5 mm 2 / s or more 4.0mm 2 / s or less, preferably 3.0 mm 2 / s or more 3.9mm 2 / s or less, preferably 3.2 mm 2 / s or more 3.8mm 2 / s or less, and more preferably 3.4 mm 2 / s or more 3.6mm 2 The kinetic viscosity of the lubricating base oil at 100°C is 4.0 mm 2 By ensuring that the kinetic viscosity of the lubricating base oil at 100°C is 2.5 mm / s or less, sufficient fuel saving performance can be obtained. 2 / s or more, the formation of an oil film at the lubricated portion can be ensured, and the evaporation loss of the lubricating oil composition can also be reduced. The kinematic viscosity at 100°C refers to the kinematic viscosity of all the lubricating base oils mixed together, i.e., the kinematic viscosity of the base oil as a whole, and does not refer to the kinematic viscosity of a specific lubricating base oil when multiple base oils are included. In this specification, the term "kinematic viscosity at 100°C" means the kinematic viscosity at 100°C measured in accordance with ASTM D-445.

[0015] In the lubricating oil composition of the present invention, the content of the lubricating base oil is, for example, 50 mass % or more and 95 mass % or less, preferably 60 mass % or more and 95 mass % or less, more preferably 70 mass % or more and 95 mass % or less, even more preferably 80 mass % or more and 95 mass % or less, and most preferably 85 mass % or more and 95 mass % or less, based on the total amount of the lubricating oil composition.

[0016] [B] Magnesium salicylate In the lubricating oil composition of the present invention, magnesium salicylate is used as the metallic detergent. In addition to magnesium salicylate, other metallic detergents may be contained, but it is preferred to contain only magnesium salicylate.

[0017] An example of magnesium salicylate is a compound represented by the following formula (1).

[0018] [ka]

[0019] In the formula (1), R 1 Each independently represents an alkyl or alkenyl group having 14 to 30 carbon atoms, and n represents 1 or 2. Mg represents magnesium. n is preferably 1. When n=2, R 1 may be a combination of different groups. The magnesium salicylate may be overbased with a carbonate or it may be overbased with a borate.

[0020] The content of magnesium salicylate contained in the lubricating oil composition of the present invention is 0.1 mass% or more, preferably 0.2 mass% or more, more preferably 0.5 mass% or more, and even more preferably 1 mass% or more, based on the total amount of the lubricating oil composition. The upper limit is 10 mass% or less, preferably 8 mass% or less, more preferably 5 mass% or less, and even more preferably 4 mass% or less. The specific range is 0.1 mass% or more and 10 mass% or less, preferably 0.2 mass% or more and 8 mass% or less, more preferably 0.5 mass% or more and 5 mass% or less, and even more preferably 1 mass% or more and 4 mass% or less. By having a magnesium salicylate content of 0.1 mass% or more, effective fuel saving performance and cleaning effect can be obtained, and by having a magnesium salicylate content of 10 mass% or less, both fuel saving performance and LSPI reduction effect can be achieved.

[0021] The amount of magnesium derived from magnesium salicylate contained in the lubricating oil composition of the present invention is preferably 500 mass ppm or more, more preferably 1000 mass ppm or more, based on the total amount of the lubricating oil composition. The upper limit is preferably 2000 mass ppm or less, more preferably 1600 mass ppm or less. The specific range is preferably 500 mass ppm or more and 2000 mass ppm or less, more preferably 1000 mass ppm or more and 1600 mass ppm or less. By keeping the magnesium content within the above range, it is possible to maintain high cleanliness inside the engine while suppressing the occurrence of LSPI.

[0022] (Base Number) The base number of the magnesium salicylate contained in the lubricating oil composition of the present invention is preferably 140 mgKOH / g or more, more preferably 180 mgKOH / g or more, and even more preferably 200 mgKOH / g or more, from the viewpoint of further improving fuel economy. The upper limit is preferably 500 mgKOH / g or less, more preferably 400 mgKOH / g or less, and even more preferably 350 mgKOH / g or less. The specific range is preferably 140 mgKOH / g or more and 500 mgKOH / g or less, more preferably 180 mgKOH / g or more and 400 mgKOH / g or less, and even more preferably 200 mgKOH / g or more and 350 mgKOH / g or less. The base number is a value measured according to JIS K 2501 5.2.3. The lower the base number, the less the inhibitory effect of MgCO3, and the further improved fuel economy can be achieved.

[0023] The lubricating oil composition of the present invention may contain metal-based detergents other than magnesium salicylate, such as phenate-based detergents, sulfonate-based detergents, and salicylate-based detergents other than magnesium salicylate, within the range that does not impair the effects of the present invention, but it is preferable that the composition contains only magnesium salicylate.

[0024] The present inventors have found that it is possible to prepare a lubricating oil composition for internal combustion engines that combines the effect of reducing LSPI and fuel economy performance by using magnesium salicylate as a detergent and further adjusting the HTHS viscosity at 150°C to 1.6 mPa·s or more and 2.5 mPa·s or less. Such a lubricating oil composition for internal combustion engines could not be obtained by using a magnesium-containing metallic detergent other than magnesium salicylate. This is surprising (see Examples and Comparative Examples described later).

[0025] [C] Viscosity index improver The lubricating oil composition of the present invention preferably contains a viscosity index improver. Viscosity index improvers that are generally used in the field of lubricating oil compositions for internal combustion engines can be used. Specifically, polymethacrylate, olefin copolymer, polybutene, polyisobutene, polyisobutylene, polystyrene, ethylene-propylene copolymer, styrene-diene copolymer and hydrogenated products thereof can be used. Polymethacrylate is preferred.

[0026] The weight average molecular weight of the viscosity index improver contained in the lubricating oil composition of the present invention is preferably 10,000 or more, more preferably 50,000 or more, and even more preferably 100,000 or more. The upper limit is preferably 800,000 or less, more preferably 500,000 or less, and even more preferably 400,000 or less. The specific range is preferably 10,000 or more and 800,000 or less, more preferably 50,000 or more and 500,000 or less, and even more preferably 100,000 or more and 400,000 or less. The weight average molecular weight of each polymer means a value determined by gel permeation chromatography (GPC) (molecular weight obtained in terms of polystyrene).

[0027] The content of the viscosity index improver contained in the lubricating oil composition of the present invention is preferably adjusted appropriately so that the HTHS viscosity of the lubricating oil composition at 150°C is 1.6 mPa·s or more and 2.5 mPa·s or less. When the viscosity index improver is contained in the lubricating oil composition of the present invention, the content thereof is 0.1 mass% or more, preferably 0.2 mass% or more, more preferably 0.5 mass% or more, and even more preferably 1 mass% or more based on the total amount of the lubricating oil composition. The upper limit is 10 mass% or less, preferably 8 mass% or less, more preferably 5 mass% or less, and even more preferably 3 mass% or less. The specific range is 0.1 mass% or more and 10 mass% or less, preferably 0.2 mass% or more and 8 mass% or less, more preferably 0.5 mass% or more and 5 mass% or less, and even more preferably 1 mass% or more and 3 mass% or less.

[0028] [D] Molybdenum-based friction modifier The lubricating oil composition of the present invention preferably further comprises (D) a molybdenum-based friction modifier as a friction modifier. Component (D) is preferably molybdenum dithiocarbamate (hereinafter sometimes simply referred to as MoDTC).

[0029] As MoDTC, for example, a compound represented by the following formula (2) can be used.

[0030] [ka]

[0031] In the formula (2), R 2 ~R 5 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. In addition, "(alkyl)aryl group" means "aryl group or alkylaryl group." In the alkylaryl group, the alkyl group may be substituted at any position on the aromatic ring. X 1 ~X 4 are each independently a sulfur atom or an oxygen atom, and X 1 ~X 4 At least one of the is a sulfur atom.

[0032] Examples of molybdenum-based friction modifiers other than MoDTC include molybdenum dithiophosphate, molybdenum oxide, molybdic acid, molybdates such as ammonium salts, molybdenum disulfide, molybdenum sulfide, molybdic sulfide, and sulfur-containing organic molybdenum compounds.

[0033] When the lubricating oil composition of the present invention contains a molybdenum-based friction modifier, the content thereof is 0.01 mass% or more, preferably 0.1 mass% or more, more preferably 0.2 mass% or more, and even more preferably 0.5 mass% or more, based on the total amount of the lubricating oil composition. The upper limit is 10 mass% or less, preferably 8 mass% or less, more preferably 5 mass% or less, and even more preferably 2 mass% or less. The specific range is 0.01 mass% or more and 10 mass% or less, preferably 0.1 mass% or more and 8 mass% or less, more preferably 0.5 mass% or more and 5 mass% or less, and even more preferably 0.5 mass% or more and 2 mass% or less.

[0034] The amount of molybdenum derived from the molybdenum-based friction modifier contained in the lubricating oil composition of the present invention is preferably 100 mass ppm or more, more preferably 500 mass ppm or more, based on the total amount of the lubricating oil composition. The upper limit is preferably 2000 mass ppm or less, more preferably 1000 mass ppm or less. The specific range is preferably 100 mass ppm or more and 2000 mass ppm or less, more preferably 500 mass ppm or more and 1000 mass ppm or less. By having the molybdenum content be equal to or more than the lower limit, the fuel saving performance and the LSPI suppression ability can be further improved. In addition, by having the molybdenum content be equal to or less than the upper limit, the storage stability of the lubricating oil composition can be improved.

[0035] (Other additives) The lubricating oil composition of the present invention may further comprise an antiwear agent, an antioxidant or a dispersant.

[0036] As the anti-wear agent, it is preferable to add zinc dialkyldithiophosphate (ZnDTP). For example, the zinc dialkyldithiophosphate may be a compound represented by the following general formula (3):

[0037] [ka]

[0038] R in the general formula (3) 6 ~R9 are each independently a hydrogen atom or a linear or branched alkyl group having 1 to 24 carbon atoms; R 6 ~R 9 At least one of them is a straight-chain or branched alkyl group having a carbon number of 1 to 24. This alkyl group may be primary, secondary, or tertiary. In the lubricating oil composition of the present invention, these zinc dialkyldithiophosphates may be used alone or in combination of two or more. 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, those mainly composed of zinc dithiophosphate having a secondary alkyl group are preferred because they enhance wear resistance.

[0039] When the lubricating oil composition of the present invention contains zinc dialkyldithiophosphate, its content is 0.01 mass% or more, preferably 0.1 mass% or more, more preferably 0.2 mass% or more, and even more preferably 0.5 mass% or more based on the total amount of the lubricating oil composition. The upper limit is 10 mass% or less, preferably 8 mass% or less, more preferably 5 mass% or less, and even more preferably 2 mass% or less. The specific range is 0.01 mass% or more and 10 mass% or less, preferably 0.1 mass% or more and 8 mass% or less, more preferably 0.5 mass% or more and 5 mass% or less, and even more preferably 0.5 mass% or more and 2 mass% or less.

[0040] The amount of phosphorus derived from zinc dialkyldithiophosphate contained in the lubricating oil composition of the present invention is preferably 100 mass ppm or more, more preferably 500 mass ppm or more, based on the total amount of the composition. The upper limit is preferably 2000 mass ppm or less, more preferably 1000 mass ppm or less. The specific range is preferably 100 mass ppm or more and 2000 mass ppm or less, more preferably 500 mass ppm or more and 1000 mass ppm or less.

[0041] As the antioxidant, known antioxidants such as phenol-based antioxidants and amine-based antioxidants can be used. Examples include amine-based antioxidants such as alkylated diphenylamine, phenyl-α-naphthylamine, and alkylated-α-naphthylamine, and phenol-based antioxidants such as 2,6-di-t-butyl-4-methylphenol and 4,4'-methylenebis(2,6-di-t-butylphenol). When the lubricating oil composition contains an antioxidant, the content thereof is usually 5.0 mass % or less, preferably 3.0 mass % or less, and also preferably 0.1 mass % or more, more preferably 0.5 mass % or more, based on the total amount of the lubricating oil composition.

[0042] Dispersants include ashless dispersants such as succinimides or benzylamines. When the lubricating oil composition contains a dispersant, the content thereof is usually 5.0 mass % or less, and preferably 0.1 mass % or more, based on the total amount of the lubricating oil composition.

[0043] The lubricating oil composition of the present invention may further contain other additives commonly used in lubricating oils depending on the purpose in order to improve its performance, such as antiwear or extreme pressure agents, pour point depressants, corrosion inhibitors, rust inhibitors, metal deactivators, antifoaming agents, etc.

[0044] (Lubricating oil composition for internal combustion engines) The lubricating oil composition of the present invention has an HTHS viscosity of 1.6 mPa·s or more and 2.5 mPa·s or less at 150°C. By having an HTHS viscosity of 2.5 mPa·s or less at 150°C, good fuel saving performance can be obtained. If the HTHS viscosity is less than 1.6 mPa·s, there is a possibility that lubricity will be insufficient. The lubricating oil composition of the present invention has an HTHS viscosity at 150°C of 1.6 mPa·s or more and 2.5 mPa·s or less, preferably 1.6 mPa·s or more and 2.4 mPa·s or less, more preferably 1.6 mPa·s or more and 2.3 mPa·s or less, more preferably 1.6 mPa·s or more and 2.2 mPa·s or less, even more preferably 1.6 mPa·s or more and 2.1 mPa·s or less, and most preferably 1.6 mPa·s or more and 2.0 mPa·s or less. The HTHS viscosity at 150°C refers to the high temperature high shear viscosity at 150°C as specified in ASTM D 4683.

[0045] The viscosity index of the lubricating oil composition of the present invention is preferably from 120 to 220, more preferably from 140 to 200. By having a viscosity index of 140 or more, it is possible to further improve fuel economy performance while maintaining a low HTHS viscosity at 150° C. In addition, if the viscosity index of the lubricating oil composition exceeds 220, there is a risk of volatility being deteriorated. In this specification, the viscosity index means a viscosity index measured in accordance with JIS K 2283-1993.

[0046] The lubricating oil composition of the present invention preferably has a kinematic viscosity at 40° C. of 10 mm 2 / s or more, preferably 14 mm 2 / s or more, preferably 16 mm 2 / s or more, most preferably 18 mm 2 / s or more. The upper limit is preferably 30 mm 2 / s or less, preferably 28 mm 2 / s or less, more preferably 25 mm 2 / s or less, most preferably 22 mm 2 / s or less. The specific range is preferably 10 mm 2 / s or more 30mm 2 / s or less, preferably 14 mm 2 / s or more 28mm 2 / s or less, and more preferably 16 mm 2 / s or more 25mm 2 / s or less, most preferably 18 mm 2 / s or more 22mm 2 The lubricating oil composition has a kinetic viscosity of 30 mm / s or less at 40°C. 2 When the kinematic viscosity of the lubricating oil composition at 40° C. is 10 mm / s or less, sufficient fuel saving performance can be obtained. 2 / s or more, oil film formation at lubricated points can be ensured and evaporation loss of the lubricating oil composition can be reduced. In this specification, the term "kinematic viscosity at 40°C" means the kinematic viscosity at 40°C measured in accordance with ASTM D-445.

[0047] The lubricating oil composition of the present invention preferably has a kinematic viscosity at 100°C of 3mm 2 / s or more, more preferably 4mm 2 / s or more. The upper limit is preferably 7 mm 2 / s or less, preferably 5 mm 2 / s or less. The specific range is preferably 3 mm 2 / s or more 7mm 2 / s or less, more preferably 4mm 2 / s or more 5mm 2 / s or less.

[0048] The density (ρ 15 ) is preferably 0.860 or less, more preferably 0.850 or less. In this specification, the density at 15° C. means the density measured at 15° C. in accordance with JIS K 2249-1995.

[0049] By using the lubricating oil composition of the present invention, the frequency of occurrence of LSPI can be reduced. In this specification, the frequency of occurrence of LSPI means the frequency of occurrence of abnormal combustion when the engine is running at low speed. Non-Patent Document 1 reports that the frequency of LSPI occurrence when a lubricating oil composition is used to lubricate an internal combustion engine is positively correlated with the Ca content of the lubricating oil composition and negatively correlated with the P content and Mo content of the lubricating oil composition. More specifically, it reports that an index of LSPI frequency can be estimated by the following regression equation (6) based on the contents of each element in the lubricating oil composition. Formula (6) LSPI frequency index = 6.59 x Ca - 26.6 x P - 5.12 x Mo + 1.69 (In formula (6), Ca represents the calcium content (% by mass) in the composition, P represents the phosphorus content (% by mass) in the composition, and Mo represents the molybdenum content (% by mass) in the composition.)

[0050] The LSPI frequency index (calculated value) according to formula (6) of the lubricating oil composition of the present invention is preferably 0 or less, more preferably 0.1 or less, more preferably 0.2 or less, more preferably 0.3 or less, more preferably 0.4 or less, even more preferably 0.5 or less, and most preferably 0.6 or less.

[0051] The NOACK evaporation loss of the lubricating oil composition of the present invention at 250°C is preferably 30% by mass or less, more preferably 20% by mass or less, and particularly preferably 15% by mass or less. If the NOACK evaporation loss of the lubricating oil base oil component exceeds 30% by mass, the evaporation loss of the lubricating oil is large, which is undesirable as it may cause an increase in viscosity. In this specification, the NOACK evaporation loss is the amount of evaporation of the lubricating oil measured in accordance with ASTM D 5800. The lower limit of the NOACK evaporation amount of the lubricating oil composition at 250°C is not particularly limited, but is usually 5% by mass or more. EXAMPLES

[0052] The present invention will be described below with reference to examples. The present invention is not limited to the following embodiments. Note that % indicates % by mass unless otherwise specified.

[0053] <Lubricant blend> For each Example and Comparative Example, a test lubricating oil composition was prepared by blending the base oil and additives in the blending ratios shown in Tables 1 and 2. The obtained test lubricating oil compositions were evaluated as follows. The evaluation results are shown in Tables 1 and 2.

[0054] (A) Base oil Base oil 1: Group II Base oil (mineral oil) Kinematic viscosity 3.3mm 2 / s(100℃), viscosity index 112 Base oil 2: Group III base oil (mineral oil) kinematic viscosity 4.3mm 2 / s(100℃), viscosity index 123 Lubricating base oils were prepared by mixing base oils in the mass ratios shown in Tables 1 and 2. In the tables, the values ​​of the base oils indicate mass ratios based on the total amount of the base oils.

[0055] (2) Additives Additives were added as shown in Tables 1 and 2. Details of the additives are as follows: The blending amount of the additives is based on the total amount of the lubricating oil composition. (B) Metallic detergents Metallic detergent 1: Calcium salicylate (calcium content 8.0% by mass, base number: 225 mg KOH / g) Metallic detergent 2: Calcium sulfonate (calcium content 12.5 mass%, base number: 320 mgKOH / g) Metallic detergent 3: Magnesium salicylate (magnesium content 7.4% by mass, base number: 342 mg KOH / g) Metallic detergent 4: Magnesium salicylate (magnesium content 6.1% by mass, base number: 292 mg KOH / g) Metallic detergent 5: Magnesium salicylate (magnesium content 4.3% by mass, base number: 218 mg KOH / g) Metallic detergent 6: Magnesium salicylate (magnesium content 8.3% by mass, base number: 390 mgKOH / g) Metallic detergent 7: Magnesium sulfonate (magnesium content 9.1% by mass, base number: 405 mg KOH / g) (C) Viscosity index improver Viscosity index improver 1: Polymethacrylate (weight average molecular weight 380,000) (D) Friction modifier Friction modifier 1: Molybdenum dithiocarbamate (molybdenum content 9.1% by mass, sulfur content 10.8% by mass)

[0056] Antiwear agent 1: Zinc dialkyldithiophosphate (zinc content 9.3% by mass, phosphorus content 9.3% by mass, sulfur content 17.6% by mass, secondary ZnDTP) Dispersant 1: Succinic acid polyimide (nitrogen content 1.75% by mass) Antioxidant 1: Amine-based antioxidant Antioxidant 2: Phenolic antioxidant

[0057] <Evaluation method> (1) Fuel efficiency A motoring engine torque test was carried out for each test lubricating oil composition. For each test lubricating oil composition, the torque required to rotate the output shaft of a DOHC engine (displacement: 2.0 L) lubricated with the lubricating oil composition (oil temperature: 95° C.) at a constant speed by an electric motor was measured. The measurement was carried out at 1000 rpm, and the torque reduction rate was calculated relative to the measured value in Comparative Example 1. A higher torque reduction rate indicates better fuel economy performance.

[0058] (2) LSPI frequency calculation value The LSPI frequency index for each test lubricating oil composition was calculated using the above-mentioned formula (6). The lower the LSPI frequency index, the better the LSPI inhibition ability.

[0059] The evaluation results of each test lubricating oil composition are shown in the following Tables 1 and 2. The density at 15° C. of each of the test lubricating oil compositions of Examples 1 to 4 and Comparative Examples 1 to 7 was 0.850 or less.

[0060] [Table 1]

[0061] [Table 2]

[0062] Examples 1 to 4, in which magnesium salicylate was used as a metal-based detergent and the HTHS viscosity at 150° C. was adjusted to 1.7, showed improved fuel economy performance and lower LSPI frequency calculation values ​​than Comparative Example 1. Comparative Example 1, in which calcium salicylate was used as the metal-based detergent, had a high calculated LSPI frequency. In Comparative Example 2, in which the HTHS viscosity at 150° C. was adjusted to 2.6, the fuel economy performance was worse than that of Comparative Example 2. Comparative Example 3, in which calcium salicylate was used as a metal-based detergent and the HTHS viscosity at 150° C. was adjusted to 2.6, exhibited worse fuel economy performance than Comparative Example 1 and a higher calculated LSPI frequency. In Comparative Example 4, in which magnesium sulfonate was used as the metal-based detergent, the fuel economy performance was deteriorated. Comparative Example 5, in which calcium salicylate was used as the metal detergent and the amount of molybdenum friction modifier added was reduced, had a high calculated LSPI frequency. In Comparative Example 5, in which calcium sulfonate was used as the metal-based detergent, the fuel economy performance deteriorated and the calculated LSPI frequency value increased. In Comparative Example 6, in which calcium sulfonate was used as a metal-based detergent and the HTHS viscosity at 150°C was adjusted to 1.6, the fuel economy performance deteriorated and the calculated LSPI frequency value increased. [Industrial Applicability]

[0063] According to the lubricating oil composition for internal combustion engines of the present invention, it is possible to provide a lubricating oil composition for internal combustion engines which combines good fuel economy performance and an effect of reducing LSPI.

Claims

1. (A) a mixture containing one or more mineral base oils and having a kinematic viscosity of 2.5 mm at 100°C ２ / s or more 4.0mm ２ / s or less of a lubricating oil base oil; (B) magnesium salicylate in an amount of 0.1% by mass or more and 10% by mass or less based on the total amount of the composition; (C) a viscosity index improver, and (D) Molybdenum-based friction modifier A lubricating oil composition for an internal combustion engine for a downsizing turbo engine, comprising: The HTHS viscosity at 150°C is 1.6 mPa·s or more and 2.5 mPa·s or less, (B) the content of the mineral oil-based base oil is 50% by mass or more based on the lubricating base oil; The content of magnesium salicylate is 0.1% by mass or more and 3.0% by mass or less based on the total amount of the composition, (C) the content of the viscosity index improver is 0.1% by mass or more and 10% by mass or less based on the total amount of the composition; (D) The lubricating oil composition for internal combustion engines for downsizing turbo engines, wherein the content of a molybdenum-based friction modifier is 0.01 mass % or more and 10 mass % or less based on the total amount of the composition.

2. 2. The lubricating oil composition for an internal combustion engine for a downsizing turbo engine according to claim 1, wherein the magnesium salicylate has a base number of 350 mg KOH / g or less.

3. 3. The lubricating oil composition for internal combustion engines for downsizing turbo engines according to claim 1 or 2, having a HTHS viscosity at 150° C. of 1.6 mPa·s or more and 2.0 mPa·s or less.

4. The lubricating oil composition for internal combustion engines for downsizing turbo engines according to any one of claims 1 to 3, wherein the LSPI frequency index calculated by the following formula (6) is 0 or less. Formula (6) LSPI frequency index = 6.59 x Ca - 26.6 x P - 5.12 x Mo + 1.69 (In formula (6), Ca represents the calcium content (% by mass) in the composition, P represents the phosphorus content (% by mass) in the composition, and Mo represents the molybdenum content (% by mass) in the composition.)

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