Lubricating oil composition for internal combustion engines

Abstract

To provide a lubricant for internal combustion engines that has excellent fuel efficiency at a low oil-temperature as well as at a high oil-temperature.SOLUTION: A lubricant composition for internal combustion engines contains (A) a lubricant base oil and, as metal sanitizers, (B) calcium borate salicylate and (C) magnesium salicylate. The amount of calcium derived from (B) calcium borate salicylate is 300 mass ppm or more and 1200 mass ppm or less relative to the total amount of the lubricant composition.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a lubricating oil composition for internal combustion engines, and more particularly to a lubricating oil composition for internal combustion engines that exhibits excellent fuel economy both at high oil temperatures and at low oil temperatures. [Background technology]

[0002] Since its invention, internal combustion engines have been the power source for various means of transportation for many years. In recent years, the fuel efficiency required for internal combustion engines has been increasing. To meet this demand, high fuel efficiency performance is also required for lubricating oils for internal combustion engines.

[0003] Various studies have been conducted to improve the fuel economy performance of lubricating oils for internal combustion engines. For example, Patent Document 1 discloses a lubricating oil for internal combustion engines that employs a specific blend of metal-based detergents to ensure LSPI inhibition and cleaning performance while improving fuel economy performance. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2017-226793 A Summary of the Invention [Problem to be solved by the invention]

[0005] The lubricating oil for internal combustion engines described in Patent Document 1 aims to improve fuel efficiency performance at high oil temperatures, and no consideration has been given to improving fuel efficiency performance at low oil temperatures. By improving fuel efficiency performance not only at high oil temperatures but also at low oil temperatures, it is possible to obtain a lubricating oil for internal combustion engines with better fuel efficiency. [Means for solving the problem]

[0006] The present inventors have conducted extensive research into lubricating oils for internal combustion engines that are excellent in fuel efficiency not only at high oil temperatures but also at low oil temperatures. In the prior art, it was believed that the more calcium borate salicylate was added, the better the fuel efficiency at high oil temperatures. However, the present inventors have newly discovered that an excessive amount of calcium borate salicylate adversely affects fuel efficiency at low oil temperatures. The present inventors have also confirmed that a combination of calcium borate salicylate and magnesium salicylate can provide a lubricating oil for internal combustion engines that is excellent in fuel efficiency not only at high oil temperatures but also at low oil temperatures, and have thus completed the present invention.

[0007] The present invention has been made based on such findings and is as follows. <1> (A) Lubricant base oil; Metallic detergents include (B) calcium borate salicylate and (C) magnesium salicylate. (B) a calcium content derived from calcium borate salicylate is 300 ppm by mass or more and 1,200 ppm by mass or less based on the total amount of the lubricating oil composition. <2> The HTHS viscosity at 150°C is 1.6 mPa s or more and 2.3 mPa s or less. <1> The lubricating oil composition for internal combustion engines according to claim 1. <3> (B) the content of boron derived from calcium borate salicylate is 100 ppm by mass or more and 600 ppm by mass or less based on the total amount of the lubricating oil composition; <1> or <2> The lubricating oil composition for internal combustion engines according to claim 1. <4> (C) the content of magnesium derived from magnesium salicylate is 100 ppm by mass or more and 1000 ppm by mass or less based on the total amount of the lubricating oil composition; <1> ~ <3> 2. The lubricating oil composition for internal combustion engines according to claim 1 . <5> (A) The kinetic viscosity of the lubricating base oil at 100°C is 3.0 mm 2 / s or more 5.0mm 2 / s or less, <1> ~ <4> 2. The lubricating oil composition for internal combustion engines according to claim 1 . <6> (D) a molybdenum-based friction modifier is further contained in an amount of 100 ppm by mass or more and 1000 ppm by mass or less in terms of molybdenum, based on the total amount of the composition; <1> ~ <5> 2. The lubricating oil composition for internal combustion engines according to claim 1 . Effect of the Invention

[0008] The lubricating oil composition for internal combustion engines of the present invention can provide a lubricating oil for internal combustion engines that exhibits excellent fuel economy not only at high oil temperatures but also at low oil temperatures. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] [A] Lubricant base oil The lubricating base oil used in the present invention may be either a mineral oil or a synthetic base oil, and it is preferred to use a mineral oil as the lubricating base oil in the present invention.

[0010] As the mineral oil, a distillate oil obtained by distilling crude oil at atmospheric pressure can be used. In addition, a lubricating oil fraction prepared by subjecting the distillate oil obtained by further distilling the distillate oil under reduced pressure to various refining processes can also be used. As the refining process, hydrorefining, solvent extraction, solvent dewaxing, hydrodewaxing, sulfuric acid washing, clay treatment, etc. can be appropriately combined. By combining and processing these refining processes in an appropriate order, a lubricating oil base oil that can be used in the present invention can 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 can also be used.

[0011] 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.

[0012] 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.

[0013] In the lubricating oil composition of the present invention, a synthetic base oil may be used as the lubricating oil base oil. Examples of synthetic base oils include polyα-olefins and their hydrogenated products, isobutene oligomers and their hydrogenated products, isoparaffins, alkylbenzenes, alkylnaphthalenes, diesters (ditridecyl glutarate, di-2-ethylhexyl adipate, diisodecyl adipate, ditridecyl adipate, di-2-ethylhexyl sebacate, etc.), polyol esters (trimethylolpropane caprylate, trimethylolpropane pelargonate, pentaerythritol 2-ethylhexanoate, pentaerythritol pelargonate, etc.), polyoxyalkylene glycols, dialkyl diphenyl ethers, polyphenyl ethers, and mixtures thereof. Among these, polyα-olefins are preferred. Polyα-olefins typically include oligomers or cooligomers of α-olefins having 2 to 32 carbon atoms, preferably 6 to 16 carbon atoms (such as 1-octene oligomer, decene oligomer, ethylene-propylene cooligomer, etc.), and hydrogenated products thereof.

[0014] The kinematic viscosity at 100°C of the lubricating base oil contained in the lubricating oil composition of the present invention is 3.0 mm 2 / s or more 5.0mm 2 The kinematic viscosity of the lubricating base oil of the present invention at 100° C. is preferably 3.2 mm 2 / s or more, preferably 3.5 mm 2 / s or more, more preferably 4.0 mm 2 / s or more. The upper limit is preferably 4.8 mm 2 / s or less, preferably 4.6 mm 2 / s or less, more preferably 4.5 mm 2 / s or less, most preferably 4.3 mm 2 / s or less. The specific range is preferably 3.2 mm 2 / s or more 4.8mm 2 / s or less, preferably 3.5 mm 2 / s or more 4.6mm 2 / s or less, more preferably 4.0 mm 2 / s or more 4.5mm 2 / s or less, most preferably 4.0 mm 2 / s or more 4.3mm 2 The kinetic viscosity of the lubricating base oil at 100°C is 5.0 mm 2 / s or less, sufficient fuel saving performance can be obtained. In addition, the kinetic viscosity of the lubricating base oil at 100°C is 3.0 mm 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] The viscosity index of the lubricating base oil contained in the lubricating oil composition of the present invention is preferably 110 or more, more preferably 120 or more. By having the viscosity index of the lubricating base oil be equal to or more than the lower limit, it is possible to improve fuel economy. The upper limit of the viscosity index of the lubricating base oil is not particularly limited, but it can usually be 160 or less. In this specification, the viscosity index means the viscosity index defined in JIS K 2283:2000.

[0016] 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.

[0017] [B] Calcium borate salicylate The lubricating oil composition of the present invention contains calcium borate salicylate as a metal detergent.

[0018] Calcium borate salicylate is calcium salicylate that has been overbased with boric acid or a borate. An example of calcium salicylate is a compound represented by the following formula (1).

[0019] [ka]

[0020] 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. Ca represents calcium. n is preferably 1. When n=2, R 1 may be a combination of different groups.

[0021] The amount of calcium derived from calcium borate salicylate contained in the lubricating oil composition of the present invention is 300 mass ppm or more and 1200 mass ppm or less based on the total amount of the lubricating oil composition. The amount of calcium derived from calcium borate salicylate is preferably 400 mass ppm or more, more preferably 500 mass ppm or more. The upper limit is preferably 1100 mass ppm or less, more preferably 1000 mass ppm or less. The specific range is preferably 400 mass ppm or more and 1100 mass ppm or less, more preferably 500 mass ppm or more and 1000 mass ppm or less. By setting the content of calcium derived from calcium borate salicylate within the above range, fuel saving can be ensured not only at high oil temperatures but also at low oil temperatures. In this specification, unless otherwise specified, the contents of calcium, magnesium, zinc, boron, and molybdenum in oil are measured by inductively coupled plasma atomic emission spectrometry (intensity ratio method (internal standard method)) in accordance with JPI-5S-62.

[0022] The amount of boron derived from calcium borate salicylate contained in the lubricating oil composition of the present invention is preferably 50 mass ppm or more, more preferably 100 mass ppm or more, and even more preferably 200 mass ppm or more, based on the total amount of the lubricating oil composition. The upper limit is preferably 800 mass ppm or less, more preferably 600 mass ppm or less, even more preferably 500 mass ppm or less, and most preferably 400 mass ppm or less. The specific range is preferably 50 mass ppm or more and 800 mass ppm or less, more preferably 100 mass ppm or more and 600 mass ppm or less, even more preferably 200 mass ppm or more and 500 mass ppm or less, and most preferably 200 mass ppm or more and 400 mass ppm or less.

[0023] (Base Number of Calcium Borate Salicylate) The base number of the calcium borate salicylate contained in the lubricating oil composition of the present invention is preferably 140 mgKOH / g or more, more preferably 160 mgKOH / g or more, and even more preferably 180 mgKOH / g or more. The upper limit is preferably 500 mgKOH / g or less, more preferably 400 mgKOH / g or less, and even more preferably 300 mgKOH / g or less. The specific range is preferably 140 mgKOH / g or more and 500 mgKOH / g or less, more preferably 160 mgKOH / g or more and 400 mgKOH / g or less, and even more preferably 180 mgKOH / g or more and 300 mgKOH / g or less. The base number is a value measured according to JIS K 2501:2003 9.

[0024] [C] Magnesium salicylate An example of magnesium salicylate is a compound represented by the following formula (2).

[0025] [ka]

[0026] In the formula (2), R 2 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 2 may be a combination of different groups. The magnesium salicylate may be overbased with a carbonate or with a borate.

[0027] The amount of magnesium derived from magnesium salicylate contained in the lubricating oil composition of the present invention is preferably 50 mass ppm or more, more preferably 100 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 50 mass ppm or more and 2000 mass ppm or less, more preferably 100 mass ppm or more and 1000 mass ppm or less. By setting the content of magnesium derived from magnesium salicylate within the above range, fuel efficiency can be further improved not only at high oil temperatures but also at low oil temperatures.

[0028] (Base Number) The base number of the magnesium salicylate contained in the lubricating oil composition of the present invention is preferably 200 mgKOH / g or more, more preferably 250 mgKOH / g or more, and even more preferably 300 mgKOH / g or more. The upper limit is preferably 600 mgKOH / g or less, more preferably 500 mgKOH / g or less, and even more preferably 400 mgKOH / g or less. The specific range is preferably 200 mgKOH / g or more and 600 mgKOH / g or less, more preferably 250 mgKOH / g or more and 500 mgKOH / g or less, and even more preferably 300 mgKOH / g or more and 400 mgKOH / g or less.

[0029] (Calcium Salicylate) The lubricating oil composition of the present invention may further contain calcium salicylate as a metal-based detergent. In this specification, "calcium salicylate" means calcium salicylate that does not contain boron or has an extremely low boron content (specifically, the amount contained in the metal-based detergent is, for example, 0.1 mass % or less). In this specification, "calcium salicylate" includes calcium salicylate overbased with carbonate. In addition, in this specification, "calcium salicylate" does not include calcium salicylate borate. An example of calcium salicylate is the compound represented by the above formula (1).

[0030] When the lubricating oil composition of the present invention contains calcium salicylate, the amount of calcium derived from calcium salicylate is preferably 100 mass ppm or more, more preferably 300 mass ppm or more, and even more preferably 500 mass ppm or more, based on the total amount of the lubricating oil composition. The upper limit is preferably 1500 mass ppm or less, more preferably 1200 mass ppm or less, and even more preferably 1000 mass ppm or less. The specific range is preferably 100 mass ppm or more and 1500 mass ppm or less, more preferably 300 mass ppm or more and 1200 mass ppm or less, and even more preferably 500 mass ppm or more and 1000 mass ppm or less.

[0031] When the lubricating oil composition of the present invention contains calcium salicylate, the content thereof is 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 preferably 10 mass% or less, more preferably 5 mass% or less, and even more preferably 2 mass% or less. The specific range is preferably 0.1 mass% or more and 10 mass% or less, more preferably 0.2 mass% or more and 5 mass% or less, and even more preferably 0.5 mass% or more and 2 mass% or less.

[0032] (Base number of calcium salicylate) The base number of the calcium salicylate contained in the lubricating oil composition of the present invention is preferably 140 mgKOH / g or more, more preferably 170 mgKOH / g or more, and even more preferably 200 mgKOH / g or more. The upper limit is preferably 500 mgKOH / g or less, more preferably 400 mgKOH / g or less, and even more preferably 300 mgKOH / g or less. The specific range is preferably 140 mgKOH / g or more and 500 mgKOH / g or less, more preferably 170 mgKOH / g or more and 400 mgKOH / g or less, and even more preferably 2000 mgKOH / g or more and 300 mgKOH / g or less.

[0033] When the lubricating oil composition of the present invention contains calcium salicylate, the total amount of calcium derived from calcium borate salicylate and calcium derived from calcium salicylate is preferably 400 mass ppm or more, more preferably 700 mass ppm or more, and even more preferably 1000 mass ppm or more, based on the total amount of the lubricating oil composition. The upper limit is preferably 1800 mass ppm or less, more preferably 1600 mass ppm or less. The specific range is preferably 400 mass ppm or more and 1800 mass ppm or less, more preferably 700 mass ppm or more and 1600 mass ppm or less, and even more preferably 1000 mass ppm or more and 1600 mass ppm or less.

[0034] The ratio of the calcium content derived from calcium salicylate to the calcium content derived from calcium borate salicylate (Ca content derived from calcium salicylate / Ca content derived from calcium salicylate) is preferably 0.40 or more and 4.0 or less, more preferably 0.50 or more and 3.0 or less, and even more preferably 0.55 or more and 2.5 or less, on a mass ppm basis.

[0035] The ratio of the magnesium content derived from (C) magnesium salicylate to the calcium content derived from calcium borate salicylate (Mg content / Ca content) is preferably 0.1 or more and 2.5 or less, more preferably 0.15 or more and 2.0 or less, and even more preferably 0.18 or more and 1.5 or less, on a ppm by mass basis. The ratio of the magnesium content derived from (C) magnesium salicylate to the boron content derived from (B) calcium borate salicylate (Mg content / B content) is preferably 0.1 or more and 5.0 or less, more preferably 0.2 or more and 4.0 or less, and even more preferably 0.4 or more and 3.5 or less, on a ppm by mass basis.

[0036] The lubricating oil composition of the present invention may contain a metal-based detergent other than magnesium salicylate and calcium borate salicylate, such as a phenate-based detergent or a sulfonate-based detergent, within a range that does not impair the effects of the present invention, but it is preferable that the lubricating oil composition contains only magnesium salicylate and calcium borate salicylate.

[0037] [D] Molybdenum-based friction modifier The lubricating oil composition of the present invention preferably further contains a molybdenum-based friction modifier, preferably molybdenum dithiocarbamate (hereinafter sometimes simply referred to as MoDTC).

[0038] As MoDTC, for example, a compound represented by the following formula (3) can be used.

[0039] [ka]

[0040] In the formula (3), R 3 ~R 6 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.

[0041] 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.

[0042] When the lubricating oil composition of the present invention contains a molybdenum-based friction modifier, the amount of molybdenum derived from the molybdenum-based friction modifier is preferably 100 mass ppm or more, more preferably 300 mass ppm or more, even more preferably 500 mass ppm or more, and most preferably 700 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, and even more preferably 800 mass ppm or less. The specific range is preferably 100 mass ppm or more and 2000 mass ppm or less, more preferably 300 mass ppm or more and 1000 mass ppm or less, even more preferably 500 mass ppm or more and 800 mass ppm or less, and most preferably 700 mass ppm or more and 800 mass ppm or less. By having the molybdenum content be equal to or more than the lower limit, the fuel saving performance 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.

[0043] (Other additives) The lubricating oil compositions of the present invention may further contain viscosity index improvers, antiwear agents, antioxidants, and dispersants.

[0044] The viscosity index improver may be any of those commonly used in the field of lubricating oil compositions for internal combustion engines, specifically, polymethacrylate, olefin copolymer, polybutene, polyisobutene, polyisobutylene, polystyrene, ethylene-propylene copolymer, styrene-diene copolymer and hydrogenated products thereof.

[0045] The weight average molecular weight of the viscosity index improver is, for example, 10,000 or more and 1,000,000 or less, 100,000 or more and 800,000 or less, or 200,000 or more and 600,000 or less. The weight average molecular weight of the viscosity index improver means a value determined by gel permeation chromatography (GPC) (molecular weight obtained in terms of polystyrene).

[0046] When the lubricating oil composition of the present invention contains a viscosity index improver, the content thereof can be appropriately adjusted so that the viscosity index of the lubricating oil composition is preferably 120 or more and 350 or less, more preferably 120 or more and 310 or less, even more preferably 130 or more and 270 or less, and most preferably 130 or more and 230 or less.

[0047] 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 (4):

[0048] [ka]

[0049] R in the general formula (4) 7 ~R 10 are each independently a straight-chain 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, those containing zinc dithiophosphate having a secondary alkyl group as the main component are preferred because they enhance abrasion resistance. In the lubricating oil composition of the present invention, these zinc dialkyldithiophosphates may be used alone or in combination of two or more.

[0050] 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, and even more preferably 600 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, and even more preferably 800 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, and even more preferably 600 mass ppm or more and 800 mass ppm or less.

[0051] The amount of zinc 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, and even more preferably 700 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 1500 mass ppm or less, and even 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 1500 mass ppm or less, and even more preferably 700 mass ppm or more and 1000 mass ppm or less.

[0052] 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.

[0053] 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.

[0054] 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.

[0055] (Lubricating oil composition for internal combustion engines) The HTHS viscosity of the lubricating oil composition of the present invention at 150°C is 1.7 mPa·s or more and 2.3 mPa·s or less, preferably 1.7 mPa·s or more and 2.2 mPa·s or less, more preferably 1.7 mPa·s or more and 2.1 mPa·s or less, and even more preferably 1.7 mPa·s or more and 2.0 mPa·s or less. By having an HTHS viscosity at 150°C of 2.3 mPa·s or less, even better fuel saving performance can be obtained. If the HTHS viscosity is less than 1.7 mPa·s, there is a possibility that lubricity will be insufficient. The HTHS viscosity at 150°C refers to the high temperature high shear viscosity at 150°C as specified in ASTM D 4683.

[0056] The viscosity index of the lubricating oil composition of the present invention is preferably 120 or more and 350 or less, more preferably 120 or more and 310 or less, even more preferably 130 or more and 270 or less, and most preferably 130 or more and 230 or less. By having a viscosity index of 120 or more of the lubricating oil composition, it is possible to further improve the fuel saving performance while maintaining a low HTHS viscosity at 150° C. Furthermore, if the viscosity index of the lubricating oil composition exceeds 350, there is a risk of the volatility being deteriorated.

[0057] 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 mm2 / s or more, preferably 18 mm 2 / s or more, most preferably 20 mm 2 / s or more. The upper limit is preferably 40 mm 2 / s or less, preferably 35 mm 2 / s or less, more preferably 30 mm 2 / s or less, most preferably 28 mm 2 / s or less. The specific range is preferably 10 mm 2 / s or more 40mm 2 / s or less, preferably 14 mm 2 / s or more 35mm 2 / s or less, and more preferably 18 mm 2 / s or more 30mm 2 / s or less, most preferably 20 mm 2 / s or more 28mm 2 The lubricating oil composition has a kinetic viscosity of 40mm / 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, more 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. In this specification, the term "kinematic viscosity at 40°C" means the kinematic viscosity at 40°C measured in accordance with ASTM D-445.

[0058] The lubricating oil composition of the present invention preferably has a kinematic viscosity at 100°C of 3.0 mm 2 / s or more, more preferably 4.0 mm 2 / s or more. The upper limit is preferably 7.0 mm 2 / s or less, preferably 6.0 mm 2 / s or less. The specific range is preferably 3.0 mm 2 / s or more 7.0mm 2 / s or less, preferably 4.0 mm 2 / s or more 6.0mm 2 The lubricating oil composition has a kinetic viscosity of 7.0 mm / s or less at 100°C. 2When the kinematic viscosity of the lubricating oil composition at 100° C. is 3.0 mm / s or less, more 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. In this specification, the term "kinematic viscosity at 100°C" means the kinematic viscosity at 100°C measured in accordance with ASTM D-445.

[0059] The density (ρ 15 ) is preferably 0.860 g / cm 3 Less than or equal to 0.850 g / cm 3 In this specification, the density at 15° C. means a density measured at 15° C. in accordance with ASTM D4052. EXAMPLES

[0060] 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.

[0061] <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.

[0062] (A) Base oil Base oil 1: Group III base oil (mineral oil) kinematic viscosity 4.2mm 2 / s(100℃), viscosity index 125

[0063] 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 Metal-based detergent 1: Calcium borate salicylate (calcium content 6.8% by mass, boron content 2.7% by mass, base number: 190 mg KOH / g) Metallic detergent 2: Calcium salicylate (calcium content 8.0% by mass, base number: 225 mg KOH / g) Metallic detergent 3: Magnesium salicylate (magnesium content 7.4% by mass, base number: 340 mgKOH / g) Metallic detergent 4: Magnesium sulfonate (magnesium content 9.1% by mass, base number: 405 mg KOH / g) (C) Anti-wear agent Antiwear agent 1: Zinc dialkyldithiophosphate (zinc content 9.3% by mass, phosphorus content 8.5% by mass, sulfur content 17.6% by mass, secondary ZnDTP) (D) Friction modifier Friction modifier 1: Molybdenum dithiocarbamate (molybdenum content 10.1% by mass, sulfur content 10.8% by mass) (E) Dispersant Dispersant 1: Alkenyl succinic acid polyalkylene polyimide (nitrogen content 1.75% by mass) (F) Antioxidants Antioxidant 1: Alkylated diphenylamine Antioxidant 2: Benzenepropanoic acid, 3,4-bis(1,1 dimethyl ethyl)-4 hydroxy-C7, C9 side chain alkyl ester

[0064] <Evaluation method> (1)Friction characteristics The friction characteristics of each test lubricating oil composition were tested. Using an MTM (Mini Traction Machine) tester (manufactured by PCS Instruments), the friction characteristics of each lubricating oil composition at a constant load-slide ratio were calculated as a friction coefficient (μ). The test conditions are shown below. In this test, the smaller the friction coefficient, the more excellent the friction characteristics. The friction coefficient is the value after sliding for 3 hours at a peripheral speed of 100 mm / s. Rolling speed: 200mm / s Load: 30N Slip rate: 50% Oil temperature: 40℃ and 100℃ At 100°C, those with a value of 0.05 or less were rated as having excellent friction properties. At 40°C, those with a value of 0.06 or less were rated as having excellent friction characteristics.

[0065] 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 5 and Comparative Examples 1 to 6 was 0.850 g / cm 3 The following is the result.

[0066] [Table 1]

[0067] [Table 2]

[0068] Examples 1 to 5, which contain calcium borate salicylate and magnesium salicylate as metal detergents and have a calcium content of 300 ppm by mass or more and 1200 ppm by mass or less based on the lubricating oil composition, showed good friction coefficient values ​​when measured at both 40°C and 100°C.

[0069] In Comparative Example 1, in which the amount of calcium derived from calcium borate salicylate was 1,300 ppm by mass based on the lubricating oil composition, the friction coefficient increased in measurements at both 40°C and 100°C. In Comparative Example 2, in which the amount of calcium derived from calcium borate salicylate was 0 ppm by mass based on the lubricating oil composition, the friction coefficient increased when measured at 40°C. In Comparative Examples 3 to 6, which did not contain magnesium salicylate, the friction coefficient increased in both measurements at 40°C and 100°C. [Industrial Applicability]

[0070] The lubricating oil composition for internal combustion engines of the present invention can provide a lubricating oil for internal combustion engines that exhibits excellent fuel economy not only at high oil temperatures but also at low oil temperatures.

Claims

1. (A) a lubricating base oil; A lubricating oil composition for internal combustion engines, comprising, as metal-based detergents, (B) calcium salicylate borate and (C) magnesium salicylate, the amount of calcium derived from the calcium borate salicylate (B) is 300 ppm by mass or more and 1,200 ppm by mass or less based on the total amount of the lubricating oil composition for internal combustion engines, the content of boron derived from the calcium borate salicylate (B) is 100 ppm by mass or more and 600 ppm by mass or less based on the total amount of the lubricating oil composition for internal combustion engines, The HTHS viscosity at 150°C is 1.7 mPa·s or more and less than 2.0 mPa·s, The lubricating oil composition for internal combustion engines, wherein the content of magnesium derived from the magnesium salicylate (C) is 100 ppm by mass or more and 1000 ppm by mass or less based on the total amount of the lubricating oil composition for internal combustion engines.

2. (A) The kinetic viscosity of the lubricating base oil at 100°C is 3.0 mm ２ / s or more 5.0mm ２ 2. The lubricating oil composition for internal combustion engines according to claim 1, wherein the viscosity of the composition is 0.1 to 1000 MPa.

3. 3. The lubricating oil composition for internal combustion engines according to claim 1 or 2, further comprising (D) a molybdenum-based friction modifier in an amount of 100 ppm by mass or more and 1,000 ppm by mass or less in terms of molybdenum, based on the total amount of the composition.

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