JP2022024285A - Lubricant composition - Google Patents

Abstract

To provide a lubricant composition having excellent fuel saving properties and low temperature viscosity properties while maintaining a moderate high temperature shear viscosity even if the viscosity is lowered and to provide a lubricant composition for an internal combustion engine as a suitable example and more preferably a lubricant composition for a diesel engine.SOLUTION: There is provided a lubricant composition comprising (A) a lubricant base oil and (B) a viscosity index improver, wherein the lubricant base oil (A) has a kinematic viscosity at 100°C of 2.0 to 10.0 mm2/s, the molybdenum content of in the lubricant composition is 100 mass ppm or more and the lubricant composition has a kinematic viscosity at 100°C of 6.9 mm2/s or more and less than 9.3 mm2/s, a CCS viscosity at -35°C of 6.2 Pa s or less and a high temperature high shear viscosity (HTHS viscosity) at 150°C of 2.6 mPa s or more.SELECTED DRAWING: None

Description

The present invention relates to a lubricating oil composition. More specifically, the present invention relates to a lubricating oil composition for an internal combustion engine, particularly a lubricating oil composition for a diesel engine.

Lubricating oil compositions are widely used in the automobile field such as for internal combustion engines, automatic transmissions, and gear oils. In recent years, it has been required to reduce the viscosity in order to improve fuel efficiency, but it is also required to have excellent low-temperature viscosity characteristics while maintaining high-temperature and high-shear viscosity. In order to achieve the above object, a lubricating oil composition in which a base oil is selected and a specific additive is combined is known. For example, Patent Document 1 discloses a lubricating oil composition comprising a base oil having a specific urea adduct value and polymethacrylate having a specific structure. Further, Patent Document 2 describes a lubricating oil composition using a polymethacrylate-based viscosity index improver whose structure is further specified.

Japanese Unexamined Patent Publication No. 2009-155639 JP-A-2015-13693

However, the lubricating oil composition as described in the above patent document still has room for improvement in terms of achieving both fuel efficiency and high-temperature shear viscosity. Therefore, the present invention relates to a lubricating oil composition having excellent fuel efficiency and low-temperature viscosity characteristics while maintaining an appropriate high-temperature shear viscosity even when the viscosity is lowered, and more preferably a lubricating oil composition for an internal combustion engine. More preferably, it is an object of the present invention to provide a lubricating oil composition for a diesel engine.

As a result of diligent studies, the present inventors have found that a lubricating oil composition containing a specific lubricating oil base oil and a viscosity index improver and limiting the amount of molybdenum to a specific amount or less can be sheared at an appropriate high temperature even if the viscosity is lowered. It has been found that while maintaining the viscosity, it is excellent in fuel saving and low temperature viscosity characteristics, and it is possible to achieve both cleanliness and friction reduction, and the above object is achieved.

That is, the present invention
A lubricating oil composition containing (A) a lubricating oil base oil and (B) a viscosity index improver, wherein the (A) lubricating oil base oil has a kinematic viscosity of 2.0 to 10.0 mm ² / s at 100 ° C. The molybdenum content in the lubricating oil composition is 100% by mass or less, and the lubricating oil composition has a kinematic viscosity at 100 ° C. of 6.9 mm ² / s or more and less than 9.3 mm ² / s. The lubricating oil having a CCS viscosity of 6.2 Pa · s or less at −35 ° C. and a high temperature high shear viscosity (HTHS viscosity) of 2.6 mPa · s or more at 150 ° C. The composition is provided.

A preferred embodiment of the present invention satisfies at least one of the following requirements (1) to (12).
(1) The (B) viscosity index improver contains (B1) polymethacrylate having a weight average molecular weight of 100,000 to 400,000, and the amount of the component (B1) is 0 with respect to the total mass of the lubricating oil composition. It is characterized by having a molecular weight of 5.5 to 5.0% by mass.
(2) The (B) viscosity index improver contains an α-olefin copolymer having (B2) SSI (shear stability index) of 20 to 30, and the amount of the component (B2) is the entire lubricating oil composition. The lubricating oil composition according to claim 1 or 2, wherein the lubricating oil composition is 0.5 to 8.0% by mass with respect to the mass of the above.
(3) The lubricating oil composition further contains (C) a metal cleaning agent, and the content of the (C) metal cleaning agent is 1,000 to 2,500 mass ppm in the lubricating oil composition in terms of metal content. It is characterized by being.
(4) The (C) metal cleaning agent contains (C2) a metal cleaning agent having calcium, and the amount of the (C2) metal cleaning agent is 500 to 1,800 mass in a lubricating oil composition in terms of calcium metal. It is characterized by being ppm.
(5) The (C) metal cleaning agent contains a metal cleaning agent having (C1) magnesium, and the amount of the metal cleaning agent having (C1) magnesium is 50 to 800 in the lubricating oil composition in terms of magnesium metal. The mass is ppm.
(6) The lubricating oil composition further contains (D) zinc dialkyldithiophosphate, and the component (D) is a dialkyl having (D1) a primary alkyl group and / or (D2) a secondary alkyl group. It is 1 or more selected from zinc dithiophosphate, and the content of the component (D) is 300 to 1,500 mass ppm in terms of phosphorus amount.
(7) The lubricating oil composition contains (D2) at least one zinc dialkyldithiophosphate having a secondary alkyl group.
(8) The molybdenum is derived from a molybdenum-containing friction modifier.
(9) The lubricating oil composition is characterized by having an HTTS viscosity of 2.9 mPa · s or less at 150 ° C.
(10) The (A) lubricating oil base oil contains mineral oil and / or GTL.
(11) A lubricating oil composition for an internal combustion engine.
(12) Lubricating oil composition for diesel engines.

The lubricating oil composition of the present invention is a lubricating oil composition excellent in fuel efficiency and low temperature viscosity characteristics while maintaining high temperature shear viscosity. In particular, it is suitable as a lubricating oil composition for an internal combustion engine and further as a lubricating oil composition for a diesel engine.

The lubricating oil composition of the present invention is characterized in that the molybdenum content in the lubricating oil composition is 100 mass ppm or less. The molybdenum is derived from a molybdenum-containing friction modifier described later in more detail. The molybdenum concentration [Mo] is preferably 0 to 100 mass ppm, preferably 0 to 50 mass ppm, more preferably 0 to 10 mass ppm, and particularly preferably the molybdenum content in the lubricating oil composition. It should be 0% by mass. If the amount of the friction modifier exceeds the above upper limit, the cleanliness deteriorates. If it is blended within the above range, good cleanliness can be obtained and a sufficient friction reducing effect can be ensured.

(A) Lubricating oil base oil The lubricating oil base oil in the present invention is not particularly limited. It may be either mineral oil or synthetic oil, and these may be used alone or in combination.

As the mineral oil, for example, the lubricating oil distillate obtained by distilling the atmospheric residual oil obtained by atmospheric distillation of crude oil under reduced pressure is subjected to solvent removal, solvent extraction, hydrocracking, solvent removal, and hydrogen. Purified by one or more treatments such as chemical refining, or wax isomerized mineral oil, GTL (Gas to Liquid) base oil, ATL (Asphalt to Liquid) base oil, vegetable oil-based base oil, or a mixture thereof. The base oil can be mentioned.

Examples of the synthetic oil include polybutene or a hydride thereof; a poly-α-olefin such as 1-octene oligomer and 1-decene oligomer or a hydride thereof; 2-ethylhexyl laurate, 2-ethylhexyl palmitate, 2-stearate. Monoesters such as ethylhexyl; diesters such as ditridecylglutarate, di-2-ethylhexyl adipate, diisodecyl adipate, ditridecyl adipate, di-2-ethylhexyl sebacate; neopentyl glycol di-2-ethylhexanoate, neopentyl Glycoldi-n-octanoate, neopentyl glycol di-n-decanoate, trimethylolpropanetri-n-octanoate, trimethylolpropanetri-n-decanoate, pentaerythritol tetra-n-pentanoate, pentaerythritol tetra-n-hexanoate, Polyol esters such as pentaerythritol tetra-2-ethylhexanoate; aromatic synthetic oils such as alkylnaphthalene, alkylbenzenes and aromatic esters, or mixtures thereof, can be exemplified.

Each of the above lubricating oil base oils preferably has a kinematic viscosity (mm ² / s) of 2.0 to 10.0 mm ² / s at 100 ° C., preferably 2.5 to 9.5 mm ² / s. , More preferably 3.0 to 9.0 mm ² / s, and most preferably 3.5 to 8.0 mm ² / s. This makes it possible to obtain a lubricating oil composition having a low viscosity, excellent lubricity, and a small evaporation loss.

The viscosity index (VI) of the lubricating oil base oil is not particularly limited, but is preferably 100 or more, more preferably 120 or more, and most preferably 130 or more. This makes it possible to reduce the viscosity at low temperatures while ensuring an oil film at high temperatures.

The lubricating oil base oil preferably contains mineral oil and / or GTL, preferably contains at least one mineral oil, and more preferably contains at least one GTL. It is more preferable to contain at least 1 mineral oil and at least 1 GTL, and particularly preferably to contain at least 1 GTL. Most preferably, it does not contain synthetic oil.

The (A) lubricating oil base oil of the present invention has a kinematic viscosity (mm ² / s) of 2.0 to 10.0 mm ² / s at 100 ° C. The kinematic viscosity (mm ² / s) at 100 ° C. is preferably 2.0 to 5.8 mm ² / s, more preferably 2.5 to 5.5 mm ² / s, and even more preferably 3.0 to 5.0 mm ² / s. s, most preferably base oil (A1) having 3.5-4.5 mm ² / s and kinematic viscosity (mm ² / s) 5.8 mm ^{2 / s> 12.0 mm 2 /} s at 100 ° C. Concomitant use with a base oil (A2) having preferably 6.5 to 10.0 mm ² / s, more preferably 7.0 to 9.0 mm ² / s, and most preferably 7.5 to 8.5 mm ² / s. Is preferable. The mass ratio of the base oil (A1) to the base oil (A2) is preferably 99: 1 to 80:20 (mass ratio) for (A1) :( A2), more preferably 98: 2 to 85:15, and further. It is preferably 97: 3 to 90:10, and particularly preferably 96: 4 to 92: 8.

(B) Viscosity Index Improver It is essential that the lubricating oil composition of the present invention contains a viscosity index improver. Examples of the viscosity index improver include polymethacrylate, dispersed polymethacrylate, olefin copolymer (polyisobutylene, ethylene-propylene copolymer), dispersed olefin copolymer, polyalkylstyrene, and styrene-butadiene hydrogenated copolymer. , Styrene-maleic anhydride copolymer, those containing stellate isoprene and the like. Further, a comb-shaped polymer containing at least a repeating unit based on a polyolefin macromer and a repeating unit based on an alkyl (meth) acrylate having an alkyl group having 1 to 30 carbon atoms in the main chain can also be used.

The viscosity index improver preferably contains (B1) polymethacrylate and / or (B2) α-olefin copolymer. The (B1) polymethacrylate preferably has a weight average molecular weight of 100,000 to 400,000, more preferably 150,000 to 350,000, and even more preferably 200,000 to 300,000. The content of polymethacrylate is preferably 0.5 to 5.0% by mass or less, more preferably 0.8 to 3.0% by mass, and further preferably 1 with respect to the total mass of the lubricating oil composition. It is preferably 0.0 to 2.0% by mass, particularly preferably 1.2 to 1.8% by mass. The polymethacrylate may be either a dispersed type or a non-dispersed type.

The (B2) α-olefin copolymer preferably has an SSI (shear stability index) of 20 to 30, more preferably 21 to 28, and even more preferably 23 to 27. The weight average molecular weight of the (B2) α-olefin copolymer is preferably 50,000 to 300,000, more preferably 80,000 to 250,000, still more preferably 100,000 to 200,000. be. The amount of the (B2) α-olefin copolymer is preferably 0.5 to 8.0% by mass, more preferably 1.0 to 7.0% by mass, based on the total mass of the lubricating oil composition. It is more preferably 2.0 to 5.0% by mass, particularly preferably 2.5 to 4.5% by mass, and most preferably 3.0 to 4.0% by mass. Examples of the α-olefin copolymer include an olefin copolymer (polyisobutylene, an ethylene-propylene copolymer) and a dispersed olefin copolymer.
In the present invention, the SSI (shear stability index) can be calculated from, for example, the following formula.
SSI = [(KV ₀ -KV ₁ ) / (KV ₀ -KV _vm )] × 100
In the above formula, KV ₀ is the value of the kinematic viscosity of the lubricating oil composition (A) containing the viscosity index improver at 100 ° C., and KV ₁ is the value of the lubricating oil composition (A) containing the viscosity index improver. It is the value of the kinematic viscosity at 100 ° C. after the shear stability test. KV _vm is the value of the kinematic viscosity of the lubricating oil composition (B) obtained by removing only the viscosity index improver from the lubricating oil composition (A) at 100 ° C. The kinematic viscosity at 100 ° C. after the shear stability test is the kinematic viscosity at 100 ° C. after performing the KRL shear stability test according to CEC L45-A-99.

In the present invention, the weight average molecular weight of the polymethacrylate and α-olefin copolymer can be measured, for example, by gel permeation chromatography under the following conditions.
<Measurement conditions for Mw of α-olefin copolymer>
Equipment: "HLC-8320" [manufactured by Tosoh Corporation]
Column: 3 "TSK gel SuperMultipore HZ-M" Measurement temperature: 40 ° C
Sample solution: 0.2 (w / v)% tetrahydrofuran solution Injection amount: 30 μl
Detection device: Refractive index detector Reference material: Polystyrene (PS t Quick MP-M)

In addition to the (B1) polymethacrylate and / or (B2) α-olefin copolymer, other viscosity index improvers described above may be contained. The amount of the other viscosity index improver may be 0.1 to 5% by mass, preferably 0.5 to 3.0% by mass, and more preferably 1. It may be 0 to 2.0% by mass.

(C) Metal Cleaner The lubricating oil composition of the present invention can contain a metal cleanser. The metal cleaning agent is generally known and is not limited, but is preferably a cleaning agent having an alkali metal or an alkaline earth metal. Examples of the metal cleaning agent include calcium salicylate, calcium sulfonate, calcium phenate, magnesium salicylate, magnesium sulfonate, magnesium phenate and the like. These may be one kind alone or a mixture of two or more kinds.
The lubricating oil composition of the present invention is characterized by containing the metal cleaning agent in the lubricating oil composition at a mass of 1,000 to 2,500 mass ppm in terms of metal amount, preferably 1,300 to 2,300. It is mass ppm, more preferably 1,400 to 2,200 mass ppm, still more preferably 1,500 to 2,000 mass ppm, and particularly preferably 1,600 to 1,800 mass ppm. Is good. When two or more kinds of metal detergents are used in combination, the total metal equivalent amount is adjusted so as to satisfy the above range.

The lubricating oil composition of the present invention preferably contains (C1) a cleaning agent having magnesium (hereinafter referred to as a magnesium-based cleaning agent), and the above-mentioned magnesium sulfonate, magnesium phenate, magnesium salicylate and the like can be used. Of these, magnesium salicylate or magnesium sulfonate is particularly preferable, and magnesium sulfonate is particularly preferable. As the magnesium-based cleaning agent, one type may be used alone, or two or more types may be mixed and used.

(C1) By containing a magnesium-based cleaning agent, high-temperature cleaning property and rust prevention property required as a lubricating oil can be ensured. It can also reduce friction and thus torque. This is particularly advantageous in terms of fuel economy characteristics.

(C1) The magnesium-based cleaning agent has a concentration [Mg] of 50 to 800 mass ppm, preferably 100 to 700 mass ppm, more preferably 200 to 600 mass ppm of magnesium with respect to the mass of the lubricating oil composition. Particularly preferably, it is added in an amount in the range of 300 to 500 mass ppm. When the amount of the magnesium-based detergent exceeds the above upper limit, the wear becomes too large, and when it falls below the above lower limit, the effect of reducing friction is low.

The (C1) magnesium-based cleaning agent is particularly preferably hyperbasic. As a result, the neutralizing property required for the lubricating oil can be ensured. When a superbasic magnesium-based cleaning agent is used, a neutral magnesium-based cleaning agent or a calcium-based cleaning agent may be mixed.

The total base value of the (C1) magnesium-based detergent is not limited, but is preferably 20 to 600 mgKOH / g, more preferably 50 to 500 mgKOH / g, and most preferably 100 to 450 mgKOH / g. As a result, the acid neutralization property, high temperature cleanliness property and rust preventive property required for the lubricating oil can be ensured. When two or more kinds of metal detergents are mixed and used, it is preferable that the base value obtained by mixing is in the above range.

The magnesium content in the (C1) magnesium-based cleaning agent is preferably 0.5 to 20% by mass, more preferably 1 to 16% by mass, and most preferably 2 to 14% by mass, but the lubricating oil composition. It may be added so that the substance contains magnesium in the above range.

The lubricating oil composition of the present invention preferably contains (C2) a cleaning agent having calcium (hereinafter referred to as calcium-based cleaning agent) alone or in combination with the above-mentioned (C1) magnesium-based cleaning agent. When the lubricating oil composition contains (C2) a calcium-based cleaning agent, the high-temperature cleaning property and rust preventive property required for the lubricating oil can be further ensured. A combination of (C1) magnesium-based cleaning agent and (C2) calcium-based cleaning agent is preferable. Further, a sodium-based cleaning agent may be contained as a metal-based cleaning agent other than the above, as long as the effect of the present invention is not impaired. The sodium-based detergent is a compound having sodium, and for example, sodium sulfonate, sodium phenate and sodium salicylate are preferable. One of these sodium-based detergents may be used alone, or two or more thereof may be mixed and used. By containing a sodium-based cleaning agent, the high-temperature cleaning property and rust preventive property required as a lubricating oil can be ensured. The sodium-based cleaning agent can be used in combination with the above-mentioned (C1) magnesium-based cleaning agent and an optional (C2) calcium-based cleaning agent. However, the amount of (C2) calcium-based cleaning agent and sodium-based cleaning agent added may be limited depending on the amount of (C1) magnesium-based cleaning agent.

Examples of the (C2) calcium-based cleaning agent include the above-mentioned calcium sulfonate, calcium phenate and calcium salicylate, preferably calcium sulfonate and calcium salicylate, and more preferably calcium salicylate. One of these (C2) calcium-based detergents may be used, or two or more of them may be mixed and used.

The content of the (C2) calcium-based cleaning agent is preferably an amount of 500 to 1,900 mass ppm in the lubricating oil composition in terms of calcium metal, more preferably 600 to 1,800 mass ppm, still more preferable. Is 800 to 1,700 mass ppm, more preferably 900 to 1,600 mass ppm, particularly preferably 1,000 to 1,500 mass, and most preferably 1,100 to 1,400 mass. However, the total amount of the calcium-based cleaning agent and the magnesium-based cleaning agent is characterized by being contained in the lubricating oil composition in an amount of 1,000 to 2,500 mass ppm as a total in terms of the amount of metal, and is preferably 1,300. In an amount of up to 2,300 mass ppm, more preferably 1,400 to 2,200 mass ppm, still more preferably 1,500 to 2,000 mass ppm, and particularly preferably 1,600 to 1,800 mass ppm. be.
More preferably, an amount satisfying the following formula (i) is preferable.
{[Mg] / ([Mg] + [Ca])} × 100 ≧ 5 (i)
Here, [Ca] indicates the concentration of calcium in terms of mass ppm with respect to the mass of the lubricating oil composition.
The value of {[Mg] / ([Mg] + [Ca])} × 100 is more preferably 10 or more, still more preferably 15 or more, and particularly preferably 20 or more. If the value is less than the above lower limit, the effect of reducing friction may be small. The upper limit of {[Mg] / ([Mg] + [Ca])} × 100 is preferably 100, more preferably 80, still more preferably 60, and most preferably 40.

(C2) The calcium-based cleaning agent is preferably overbasic. This makes it possible to secure the acid neutralization property required for the lubricating oil. When a superbasic calcium-containing detergent is used, a neutral calcium-based detergent may be used in combination.

The total base value of the (C2) calcium-based detergent is not limited, but is preferably 20 to 500 mgKOH / g, more preferably 50 to 400 mgKOH / g, and most preferably 100 to 350 mgKOH / g. Thereby, the acid neutralization property, the high temperature cleanliness property and the rust preventive property required for the lubricating oil composition can be ensured. When two or more kinds of metal detergents are mixed and used, it is preferable that the base value obtained by mixing is within the above range.

The calcium content in the (C2) calcium-based cleaning agent is preferably 0.5 to 20% by mass, more preferably 1 to 16% by mass, and most preferably 2 to 14% by mass.

(D) Zinc Dialkyl Dithiophosphate The lubricating oil composition of the present invention preferably contains a specific zinc dialkyl dithiophosphate (ZnDTP (also referred to as ZDDP)). The compound functions as an anti-wear agent and is represented by the following formula (1).

上記式（１）において、Ｒ^２及びＲ^３は、各々、互いに同一であっても異なっていてもよく、水素原子または炭素数１～２６の一価炭化水素基である。一価炭化水素基としては、炭素数１～２６の第１級（プライマリー）または第２級（セカンダリー）アルキル基；炭素数２～２６のアルケニル基；炭素数６～２６のシクロアルキル基；炭素数６～２６のアリール基、アルキルアリール基またはアリールアルキル基；またはエステル結合、エーテル結合、アルコール基またはカルボキシル基を含む炭化水素基である。Ｒ^２及びＲ^３は、好ましくは炭素数１～２６の第１級（プライマリー）または第２級（セカンダリー）アルキル基である。ここで、１級アルキル基とは、置換基Ｒ^２及びＲ^３において、ジアルキルジチオリン酸亜鉛中の酸素原子に直接結合する炭素原子が１級炭素原子であるという意味である。同様に２級アルキル基とは、置換基Ｒ^２、Ｒ^３において、ジアルキルジチオリン酸亜鉛中の酸素原子に直接結合する炭素原子が２級炭素原子であるという意味である。Ｒ^２及びＲ^３は、より好ましくは、互いに独立に、炭素数３～１２の、第１級または第２級アルキル基、炭素数８～１８のシクロアルキル基、又は炭素数８～１８のアルキルアリール基である。
ただし、本発明において、Ｒ^２及びＲ^３の少なくとも１は第１級または第２級アルキル基である。第１級アルキル基は、炭素数３～１２を有することが好ましく、より好ましくは炭素数４～１０を有する。例えば、プロピル基、ブチル基、ペンチル基、ヘキシル基、オクチル基、ノニル基、デシル基、ドデシル基、２－エチル－ヘキシル基、及び２，５－ジメチルヘキシル基等が挙げられる。第２級アルキル基は、炭素数３～１２を有することが好ましく、より好ましくは炭素数３～１０を有する。例えば、イソプロピル基、セカンダリーブチル基、イソペンチル基、及びイソヘキシル基等が挙げられる。

In the above formula (1), R ² and R ³ may be the same or different from each other, and are hydrogen atoms or monovalent hydrocarbon groups having 1 to 26 carbon atoms. The monovalent hydrocarbon group includes a primary (primary) or secondary (secondary) alkyl group having 1 to 26 carbon atoms; an alkenyl group having 2 to 26 carbon atoms; a cycloalkyl group having 6 to 26 carbon atoms; carbon. An aryl group, an alkylaryl group or an arylalkyl group having a number of 6 to 26; or a hydrocarbon group containing an ester bond, an ether bond, an alcohol group or a carboxyl group. R ² and R ³ are preferably primary (primary) or secondary (secondary) alkyl groups having 1-26 carbon atoms. Here ^, the primary alkyl group means that the carbon atom directly bonded to the oxygen atom in zinc dialkyldithiophosphate at the substituents ^R2 and R3 is a primary carbon atom. Similarly ^, the secondary alkyl group means that the carbon atom directly bonded to the oxygen atom in zinc dialkyldithiophosphate at the substituents ^R2 and R3 is a secondary carbon atom. R ² and R ³ are more preferably independent of each other, a primary or secondary alkyl group having 3 to 12 carbon atoms, a cycloalkyl group having 8 to 18 carbon atoms, or an alkyl having 8 to 18 carbon atoms. It is an aryl group.
However, in the present invention, at least 1 of R ² and R ³ is a primary or secondary alkyl group. The primary alkyl group preferably has 3 to 12 carbon atoms, more preferably 4 to 10 carbon atoms. For example, a propyl group, a butyl group, a pentyl group, a hexyl group, an octyl group, a nonyl group, a decyl group, a dodecyl group, a 2-ethyl-hexyl group, a 2,5-dimethylhexyl group and the like can be mentioned. The secondary alkyl group preferably has 3 to 12 carbon atoms, more preferably 3 to 10 carbon atoms. For example, an isopropyl group, a secondary butyl group, an isopentyl group, an isohexyl group and the like can be mentioned.

The lubricating oil composition of the present invention contains one or more selected from zinc dialkyldithiophosphates having a primary alkyl group and / or a secondary alkyl group. However, (D2) always contains zinc dialkyldithiophosphate having a secondary alkyl group. That is, the first embodiment, wherein the lubricating oil composition of the present invention contains (D1) zinc dialkyl dithiophosphate having a primary alkyl group and (D2) zinc dialkyl dithiophosphate having a secondary alkyl group. D3) A second embodiment containing zinc dialkyldithiophosphate having both a primary alkyl group and a secondary alkyl group, or (D2) containing zinc dialkyldithiophosphate having a secondary alkyl group (D1) primary. It is the third aspect which does not contain zinc dialkyldithiophosphate having an alkyl group. The first aspect and the third aspect are preferable, and the third aspect particularly preferably contains only zinc dialkyldithiophosphate having a (D2) secondary alkyl group. (D2) Good wear resistance cannot be ensured unless zinc dialkyldithiophosphate having a secondary alkyl group is contained. The lubricating oil composition of the present invention comprises (D1) zinc dialkyldithiophosphate having a primary alkyl group and (D2) zinc dialkyldithiophosphate having a secondary alkyl group in a ratio (mass) of 70: 30 to. It is characterized by containing so as to satisfy the range of 0: 100. It is preferably in the range of 65:35 to 5:95, more preferably 60:40 to 10:90, particularly preferably 50:50 to 20:80, but most preferably (D2) secondary alkyl. Only zinc dialkyldithiophosphate with a group. If the content ratio of zinc dialkyldithiophosphate having a (D1) primary alkyl group exceeds the above upper limit, the wear resistance may deteriorate, which is not preferable.

The content of zinc dialkyldithiophosphate in the lubricating oil composition is 300 to 1,500 mass ppm as the concentration [P] of zinc dialkyldithiophosphate in mass ppm with respect to the total mass of the lubricating oil composition. The amount is preferably 400 to 1,200 mass ppm, more preferably 500 to 1,000 mass ppm, and particularly preferably 600 to 900 mass ppm.

As a further preferred embodiment of the present invention, the amount of boron contained in the lubricating oil composition, (D1) zinc dialkyldithiophosphate having a primary alkyl group, and (D2) dialkyldithiophosphate having a secondary alkyl group By adjusting the relationship (combination) with the mass ratio of zinc acid, the torque reduction rate can be improved. More specifically, the amount of boron with respect to the total amount of the lubricating oil composition is in the range of 0 to 300 mass ppm, preferably 20 to 200 mass ppm, particularly preferably 50 to 150 mass ppm, and the zinc dialkyldithiophosphate is used. The composition is such that the mass ratio of the component (D1) to the component (D2) is 70:30 to 0:100, preferably 65:35 to 5:95, more preferably 60:40 to 10:90, and particularly preferably 50:50. It may be adjusted appropriately within the range satisfying to 20:80. The total amount of (D) zinc dialkyldithiophosphate may be within the above range as the total mass ppm of phosphorus. As a result, even if the viscosity of the lubricating oil composition is reduced, both good anti-friction property and anti-wear property can be achieved at the same time.

The lubricating oil composition of the present invention may further contain an anti-wear agent other than zinc dialkyldithiophosphate. For example, a compound represented by the above formula, in which R ² and R ³ are independently of each other, a hydrogen atom or a monovalent hydrocarbon group having 1 to 26 carbon atoms and not an alkyl group can be mentioned. The monovalent hydrocarbon group includes an alkenyl group having 2 to 26 carbon atoms; a cycloalkyl group having 6 to 26 carbon atoms; an aryl group having 6 to 26 carbon atoms, an alkylaryl group or an arylalkyl group; or an ester bond or an ether. A hydrocarbon group containing a bond, alcohol group or carboxyl group. R ² and R ³ are preferably a cycloalkyl group having 8 to 18 carbon atoms and an alkylaryl group having 8 to 18 carbon atoms, and each of them may be the same as or different from each other. Further, zinc dithiocarbamate (ZnDTC) may be used in combination.

Further, at least one compound selected from phosphates represented by the following formulas (2) and (3), phosphite-based phosphorus compounds, and metal salts and amine salts thereof can also be used in combination.

上記一般式（２）中、Ｒ^６は炭素数１～３０の一価炭化水素基であり、Ｒ^４及びＲ^５は互いに独立に、水素原子又は炭素数１～３０の一価炭化水素基であり、ｋは０又は１である。

In the above general formula (2), R ⁶ is a monovalent hydrocarbon group having 1 to 30 carbon atoms, and R ⁴ and R ⁵ are independent hydrogen atoms or monovalent hydrocarbon groups having 1 to 30 carbon atoms. Yes, k is 0 or 1.

上記一般式（３）中、Ｒ^９は炭素数１～３０の一価炭化水素基であり、Ｒ^７及びＲ^８は互いに独立に水素原子又は炭素数１～３０の一価炭化水素基であり、ｔは０又は１である。

In the above general formula (3), R ⁹ is a monovalent hydrocarbon group having 1 to 30 carbon atoms, and R ⁷ and R ⁸ are hydrogen atoms or monovalent hydrocarbon groups having 1 to 30 carbon atoms independently of each other. , T is 0 or 1.

In the above general formulas (2) and (3), examples of the monovalent hydrocarbon group having ¹ to 30 carbon atoms represented by ^R4 to R9 include an alkyl group, a cycloalkyl group, an alkenyl group, and an alkyl-substituted cyclo. Alkyl groups, aryl groups, alkyl substituted aryl groups, and arylalkyl groups can be mentioned. In particular, an alkyl group having 1 to 30 carbon atoms or an aryl group having 6 to 24 carbon atoms is preferable, an alkyl group having 3 to 18 carbon atoms is more preferable, and an alkyl group having 4 to 15 carbon atoms is most preferable. Is.

Examples of the phosphorus compound represented by the general formulas (2) and (3) include a phosphorous acid monoester having one hydrocarbon group having 1 to 30 carbon atoms and a (hydrocarbyl) subphosphonic acid; the above carbon. Phosphorous acid diester having two hydrocarbon groups of 1 to 30, monothio-phosphorous acid diester, and (hydrocarbyl) phosphonic acid monoester; the above-mentioned phosphorous acid having 3 hydrocarbon groups of 1 to 30 carbon atoms. Triesters and (hydrocarbyl) phosphorous acid diesters; and mixtures thereof and the like.

The metal salt or amine salt of the phosphorus compound represented by the general formula (2) or (3) is the phosphorus compound represented by the general formula (2) or (3), and a metal oxide, a metal hydroxide, or the like. It remains after the action of a metal base such as a metal carbonate or a metal chloride, ammonia, a nitrogen compound such as an amine compound having only a hydrogen group having 1 to 30 carbon atoms or a hydroxyl group-containing hydrocarbon group in the molecule, and the like. It can be obtained by neutralizing part or all of the acidic hydrogen. Examples of the metal in the above metal base include alkali metals such as lithium, sodium, potassium and cesium, alkaline earth metals such as calcium, magnesium and barium, and heavy metals such as zinc, copper, iron, lead, nickel, silver and manganese. (However, molybdenum is excluded) and the like. Among these, alkaline earth metals such as calcium and magnesium and zinc are preferable, and zinc is particularly preferable.

As described above, the amount of zinc dialkyldithiophosphate added may be such that the phosphorus content derived from zinc dialkyldithiophosphate is within the above-mentioned specific range. When other anti-wear agents are contained, the total amount of the anti-wear agent including zinc dialkyldithiophosphate is usually 0.1 to 5% by mass, preferably 0.2 to 3% by mass in the lubricating oil composition. It may be mixed with.

(E) Ash-free dispersant The lubricating oil composition of the present invention preferably further contains an ash-free dispersant. The ashless dispersant is not particularly limited, and conventionally known ones may be used. Examples thereof include a nitrogen-containing compound or a derivative thereof having at least one alkyl group or alkenyl group having a linear structure or a branched structure in the molecule and having 40 to 400 carbon atoms, or a modified product of alkenyl succinimide. .. One type of ashless dispersant may be used alone, or two or more types may be used in combination. When a borated ashless dispersant is used, it may be a borated version of the ashless dispersant as described above. Borylation is generally carried out by allowing boric acid to act on the nitrogen-containing compound to neutralize some or all of the remaining amino and / or imino groups.

The alkyl group or alkenyl group preferably has 40 to 400 carbon atoms, more preferably 60 to 350 carbon atoms. When the number of carbon atoms of the alkyl group and the alkenyl group is less than the above lower limit value, the solubility of the compound in the lubricating oil base oil tends to decrease. Further, when the carbon number of the alkyl group and the alkenyl group exceeds the above upper limit value, the low temperature fluidity of the lubricating oil composition tends to deteriorate. The alkyl group and the alkenyl group may have a linear structure or a branched structure. Preferred embodiments include, for example, olefin oligomers such as propylene, 1-butene, isobutylene, branched alkyl groups or branched alkenyl groups derived from ethylene and propylene co-oligomers, and the like.

The succinimide includes a so-called monotype succinimide in which succinic anhydride is added to one end of the polyamine, and a so-called bis-type succinimide in which succinic anhydride is added to both ends of the polyamine. The lubricating oil composition of the present invention may contain either monotype or bistype, or may contain both.

The monotype succinimide derivative can be represented by, for example, the following formula (a). The bis-type succinimide derivative can be represented by, for example, the following formula (b).

In the above formula, R ¹ is an alkyl group or an alkenyl group having 40 to 400 carbon atoms independently of each other, m is an integer of 1 to 20, and n is an integer of 0 to 20. In particular, a bis-type succinimide compound is preferable. The succinimide derivative may be a combination of monotype and bistype, a combination of two or more monotypes, and a combination of two or more bistypes.
By reacting the above-mentioned succinimide derivative with a boron compound, a boronized succinimide derivative can be obtained. The boron compound is boric acid, boric anhydride, boric acid ester, boron oxide, boron halide and the like. The boronized succinimide derivative may be used alone or in combination of two or more.

For example, as a method for producing a borated succinimide, it is disclosed in Japanese Patent Publication No. 42-8013, Japanese Patent Application Laid-Open No. 42-8014, Japanese Patent Application Laid-Open No. 51-52381, Japanese Patent Application Laid-Open No. 51-130408, and the like. The method used is mentioned. More specifically, an organic solvent such as alcohols, hexane, and xylene, a polyamine in a light lubricating oil base oil, and a boron compound such as boric acid, boric acid ester, or borate in polyalkenylsuccinic acid (anhydrous). It can be obtained by mixing and heat-treating under appropriate conditions. The boron content of the boronized succinimide thus obtained can be usually 0.1 to 4% by mass. In particular, a boron-modified compound (borated succinimide) of an alkenyl succinimide compound is preferable because it is excellent in heat resistance, antioxidant property and wear resistance.

The number average molecular weight (Mn) of the ashless dispersant is preferably 2000 or more, more preferably 2500 or more, still more preferably 3000 or more, most preferably 5000 or more, and 15000 or less. Is preferable. If the number average molecular weight of the ashless dispersant is less than the above lower limit, the dispersibility may not be sufficient. On the other hand, if the number average molecular weight of the ashless dispersant exceeds the above upper limit, the viscosity is too high, the fluidity becomes insufficient, and there is a possibility that the deposit may increase.

The boron content derived from the ashless dispersant with respect to the total mass of the lubricating oil composition is preferably 250 mass ppm or less, more preferably 200 mass ppm or less, and further preferably 150 mass ppm or less. When the ashless dispersant has boron, it is preferably an ashless dispersant having 1.0% by mass or less of boron, and more preferably an ashless dispersant having 0.8% by mass or less of boron. As the ashless dispersant, both a ashless dispersant containing boron and an ashless dispersant containing no boron can be used, and can be used in combination. The content of the boron-containing ashless dispersant in the lubricating oil composition depends on the boron content in the boron-containing ashless dispersant, but in particular, the blending amount of the boron-containing ashless dispersant is based on the total amount of the composition. It is preferably 0 to 5.0% by weight, preferably 0.1 to 4.0% by mass, more preferably 0.5 to 3.0% by mass, and particularly preferably 1.0 to 2.0% by mass. .. The blending amount of the ashless dispersant containing no boron is 0.1 to 10% by mass, preferably 0.5 to 9.0% by mass, and more preferably 1.0 to 8.0% by mass based on the total amount of the composition. Particularly preferably, it is 2.5 to 7.0% by mass, and most preferably 4.0 to 6.0% by mass.

(F) Friction modifier The lubricating oil composition of the present invention may further contain a friction modifier. As the friction modifier, a known molybdenum friction modifier can be used. For example, sulfur-containing organic molybdenum compounds such as molybdenum dithiophosphate (MoDTP) and molybdenum dithiocarbamate (MoDTC), complexes of molybdenum compounds with sulfur-containing organic compounds or other organic compounds, and molybdenum sulfide and molybdenum sulfide acid. Examples thereof include a complex of a sulfur-containing molybdenum compound and an alkenyl succinate imide. Examples of the molybdenum compound include molybdenum oxide such as molybdenum dioxide and molybdenum trioxide, molybdic acid such as orthomolybdic acid, paramolybdic acid and (poly) molybdate sulfide, and molybdates such as metal salts and ammonium salts of these molybdic acids. Examples thereof include molybdate sulfide such as molybdate, molybdate disulfide, molybdenum trisulfide, molybdenum pentasulfide and molybdenum polysulfide, molybdate sulfide, metal salt or amine salt of molybdate sulfide, molybdenum halide such as molybdenum chloride and the like. Examples of the sulfur-containing organic compound include alkyl (thio) xanthate, thiadiazole, thiadiazole, thiocarbonate, tetrahydrocarbylthiuram disulfide, bis (di (thio) hydrocarbyldithiophosphonate) disulfide, and organic (poly) sulfide. And sulfide ester and the like. In particular, organic molybdenum compounds such as molybdenum dithiophosphate (MoDTP) and molybdenum dithiocarbamate (MoDTC) are preferred.

Molybdenum dithiocarbamate (MoDTC) is a compound represented by the following formula [I], and molybdenum dithiophosphate (MoDTP) is a compound represented by the following [II].

In the above general formulas [I] and [II], R ₁ to R ₈ may be the same or different from each other, and are monovalent hydrocarbon groups having 1 to 30 carbon atoms. The hydrocarbon group may be linear or branched. The monovalent hydrocarbon group includes a linear or branched alkyl group having 1 to 30 carbon atoms; an alkenyl group having 2 to 30 carbon atoms; a cycloalkyl group having 4 to 30 carbon atoms; an aryl having 6 to 30 carbon atoms. Groups, alkylaryl groups, arylalkyl groups and the like can be mentioned. In the arylalkyl group, the bonding position of the alkyl group is arbitrary. More specifically, examples of the alkyl group include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, a decyl group, an undecyl group, a dodecyl group and a tridecyl group. , Tetradecyl group, pentadecyl group, hexadecyl group, heptadecyl group, octadecyl group and the like, and branched alkyl groups thereof can be mentioned, and an alkyl group having 3 to 8 carbon atoms is particularly preferable. Further, X ₁ and X ₂ are oxygen atoms or sulfur atoms, and Y ₁ and Y ₂ are oxygen atoms or sulfur atoms.

As the friction modifier, a sulfur-free organic molybdenum compound can also be used. Examples of such a compound include a molybdenum-amine complex, a molybdenum-succinic acidimide complex, a molybdenum salt of an organic acid, and a molybdenum salt of an alcohol.

Further, as the friction modifier in the present invention, the trinuclear molybdenum compound described in US Pat. No. 5,906,968 can also be used.

As described above, the present invention is characterized in that the mass ppm of molybdenum with respect to the mass of the lubricating oil composition is 100 mass ppm or less. Therefore, in the lubricating oil composition of the present invention, the amount of the molybdenum friction modifier is such that the concentration [Mo] as the mass ppm of molybdenum with respect to the mass of the lubricating oil composition is 0 mass ppm or more and 100 mass ppm or less, preferably 50 mass. The amount is ppm or less, more preferably 10% by mass or less, and particularly preferably 0% by mass. If the amount of the molybdenum-containing friction modifier exceeds the above upper limit, the cleanliness deteriorates. If it is blended within the above range, good cleanliness can be obtained and a sufficient friction reducing effect can be ensured.

The friction modifier may be used alone or in combination of two or more. The lubricating oil composition of the present invention can contain an organic friction modifier as a friction modifier other than the molybdenum friction modifier. The organic friction modifier means a friction modifier having no metal. For example, it is composed of an organic compound such as an amine-based friction modifier, an amide-based friction modifier, an ester-based friction modifier, and an ether-based friction modifier. Particularly preferably, it is an ester-based friction modifier and functions suitably as a phosphorus scavenger. If the organic friction modifier is not contained, it becomes difficult to secure excellent wear resistance and seizure resistance. The content of the organic friction modifier in the lubricating oil composition is preferably 0.1 to 2% by mass, more preferably 0.2 to 1.5% by mass, and further preferably 0.2 to 1% by mass. %. The organic friction modifier may be used alone or in combination of two or more.

Other Additives The lubricating oil composition of the present invention may further contain other additives depending on the purpose in order to improve its performance. As other additives, those generally used in lubricating oil compositions can be used, and for example, antioxidants, corrosion inhibitors, rust inhibitors, pour point depressants, anti-emulsifiers, and metal inactivations. Additives such as agents and antifoaming agents can be mentioned.

Examples of the antioxidant include ashless antioxidants such as phenol and amines, and metal-based antioxidants such as copper and molybdenum. For example, examples of the phenolic ashless antioxidant include 4,4'-methylenebis (2,6-di-tert-butylphenol), 4,4'-bis (2,6-di-tert-butylphenol), and isooctyl-. 3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate and the like, and examples of the amine-based antioxidant-free antioxidant include phenyl-α-naphthylamine, alkylphenyl-α-naphthylamine, dialkyldiphenylamine and the like. Be done. The antioxidant is usually compounded in the lubricating oil composition in an amount of 0.1 to 5% by mass.

Examples of the corrosion inhibitor include benzotriazole-based, tolyltriazole-based, thiadiazole-based, and imidazole-based compounds. Examples of the rust preventive agent include petroleum sulfonate, alkylbenzene sulfonate, dinonylnaphthalene sulfonate, alkenyl succinic acid ester, polyhydric alcohol ester and the like. The corrosion inhibitor and the rust inhibitor are usually blended in the lubricating oil composition in an amount of 0.01 to 5% by mass, respectively.

As the pour point lowering agent, for example, a polymethacrylate-based polymer compatible with the lubricating oil base oil to be used can be used. As the polymethacrylate, for example, a polymethacrylate-based polymer having a weight average molecular weight of less than 100,000, preferably 10,000 to 90,000, more preferably 20,000 to 80,000, still more preferably 30,000 to 70,000. It has a weight average molecular weight different from that of the polymethacrylate used as the viscosity index improver described above. The pour point lowering agent is usually dispensed in a lubricating oil composition in an amount of 0.01 to 3% by mass.

Examples of the anti-emulsifier include polyalkylene glycol-based nonionic surfactants such as polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, and polyoxyethylene alkyl naphthyl ether. The anti-emulsifier is usually blended in the lubricating oil composition in an amount of 0.01 to 5% by mass.

Examples of the metal inactivating agent include imidazoline, pyrimidine derivative, alkylthiadiazole, mercaptobenzothiazole, benzotriazole or its derivative, 1,3,4-thiadiazole polysulfide, 1,3,4-thiadiazole-2,5-. Examples thereof include bisdialkyldithiocarbamate, 2- (alkyldithio) benzimidazole, β- (o-carboxybenzylthio) propionnitrile and the like. The metal deactivating agent is usually blended in the lubricating oil composition in an amount of 0.01 to 3% by mass.

Examples of the defoaming agent include silicone oil having a kinematic viscosity of 1000 to 100,000 mm ² / s at 25 ° C., an alkenyl succinic acid derivative, an ester of a polyhydroxy fatty alcohol and a long chain fatty acid, methyl salicylate and o. -Hydroxybenzyl alcohol and the like can be mentioned. The defoaming agent is usually blended in the lubricating oil composition in an amount of 0.001 to 1% by mass.

Lubricating oil composition The lubricating oil composition of the present invention is required to have a kinematic viscosity at 100 ° C. in the range of 6.9 mm ² / s or more and less than 9.3 mm ² / s. It is preferably 7.2 or more and less than 9.0 mm ² / s, and more preferably 7.5 or more and less than 8.7 mm ² / s. This makes it possible to reduce the viscosity of the lubricating oil composition. This meets the requirements of SAE0W-20. The kinematic viscosity (KV100) at 100 ° C. was measured at 100 ° C. in accordance with ASTM D445.

The CCS viscosity of the lubricating oil composition of the present invention at −35 ° C. is 6.2 Pa · s or less, preferably 5.5 Pa · s or less, still more preferably 5.0 Pa · s or less, and most preferably. Is 4.5 Pa · s or less. The CCS viscosity (CCS viscosity) at −35 ° C. was measured according to ASTMD5283.

The high-temperature high-shear viscosity (HTHS viscosity) of the lubricating oil composition of the present invention at 150 ° C. is 2.6 mPa · s or more, preferably 2.7 mPa · s or more. The upper limit is preferably 2.9 mPa · s or less. The high temperature and high shear viscosity (HTHS150) at 150 ° C. was measured according to ASTMD4683.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples.

（Ｄ２）Ｓｅｃ－ＺｎＤＴＰ（上記式（１）で表され、Ｒ^２が炭素数４の第二級アルキル基であり、Ｒ^３が炭素数６の第二級アルキル基である化合物）
（Ｆ）モリブデン摩擦調整剤
モリブデンジチオカーバメート（モリブデン含有量１０質量％） The components used in the examples and comparative examples are as follows.
(A) Lubricating oil base oil (A1-1) GTL-derived base oil (kinematic viscosity at 100 ° C. = 4.1 mm ² / s, VI = 129)
(A1-2) Mineral oil (kinematic viscosity at 100 ° C. = 4.1 mm ² / s, VI = 134)
(A2-1) GTL-derived base oil (kinematic viscosity at 100 ° C. = 7.6 mm ² / s, VI = 140)
(A2-2) Mineral oil (kinematic viscosity at 100 ° C. = 7.2 mm ² / s, VI = 125)
(A2-3) Poly-α-olefin (PAO) (kinematic viscosity at 100 ° C. = 5.9 mm ² / s, VI = 132)
(B) Viscosity index improver (B1) Non-dispersive polymethacrylate (Mw = 240,000)
(B2) α-olefin copolymer (SSI = 24, Mw = 150,000)
(C) Metal detergent (C1) Magnesium sulfonate (total base value 400 mgKOH / g, magnesium content 9.4% by mass)
(C2) Calcium salicylate (total base value 146 mgKOH / g, calcium content 5.2% by mass)
(D) Anti-wear agent (D1) Pri-ZnDTP (a compound represented by the following formula (1) in which both R ² and R ³ are primary alkyl groups having 8 carbon atoms.

(D2) Sec-ZnDTP (represented by the above formula (1), R ² is a secondary alkyl group having 4 carbon atoms, and R ³ is a secondary alkyl group having 6 carbon atoms).
(F) Molybdenum friction modifier Molybdenum dithiocarbamate (molybdenum content 10% by mass)

[Other Additives 1]
Ashless dispersant (polyisobutenyl succinimide, or boronized polyisobutenyl succinimide), friction modifier (ester), antioxidant (phenol), defoamer (dimethyl silicone), pour point Defoamer (PMA with Mw <100,000) and other viscosity index improvers
[Other additives 2]
Ashless dispersant (polyisobutenyl succinimide, or boried polyisobutenyl succinimide), friction modifier (ester), antioxidant (phenol), defoamer (dimethyl silicone), pour point Defoamer (PMA with Mw less than 100,000)

Examples and Comparative Examples Lubricating oil composition by mixing lubricating oil base oil, viscosity index improver, anti-wear agent, metal cleaning agent, molybdenum friction modifier and other components in the amounts shown in Tables 1 and 2 below. The thing was prepared. The parts by mass shown in the table are parts by mass with respect to the total amount (100 parts by mass) of the lubricating oil composition. The obtained composition was measured for CCS viscosity at −35 ° C., high temperature high shear viscosity at 150 ° C. (HTHS150), and kinematic viscosity at 100 ° C. (KV100). Each measuring method is as described above. Further, the high temperature cleanliness was evaluated and the amount of sulfated ash was measured according to the following method.
The results are shown in Tables 1 and 2.

Hot tube test (evaluation of high temperature cleanliness)
A hot tube test was performed according to JPI-5S-55-99. Details of the test method are described below.
The lubricating oil composition was continuously flowed through a glass tube having an inner diameter of 2 mm at 0.3 ml / hour, air at 10 ml / sec, and the temperature of the glass tube at 280 ° C. for 16 hours. The lacquer adhering to the glass tube was compared with the color sample, and a score of 10 was given for transparent and 0 for black. The higher the score, the better the high temperature cleanliness. Those with a score of 6.0 or higher were considered as passing.

Evaluation of wear resistance The measurement was performed according to the shell four-ball test (ASTMD4172) except that the rotation speed was 1800 rpm, the load was 40 kgf, the test temperature was 90 ° C., and the test time was 30 minutes. Those with a wear mark diameter of 0.6 mm or less were regarded as acceptable.

As shown in Table 1 above, the lubricating oil compositions of Comparative Examples 4 and 5 have a kinematic viscosity of 9.3 mm ² / s or more at 100 ° C., a CCS viscosity of more than 6.2 Pa · s at −35 ° C., and 150 ° C. High temperature high shear viscosity (HTHS viscosity) of 2.9 mPa · s or more. Further, the lubricating oil compositions of Comparative Examples 1, 2 and 3 have a wear resistance of 0.6 mm or more and a high temperature cleanliness (HTT) of less than 6.0. On the other hand, the lubricating oil composition of the present invention has low temperature viscosity characteristics (CCS viscosity at −35 ° C.), high temperature viscosity characteristics (high temperature high shear viscosity at 150 ° C. (HTHS viscosity)), and wear resistance even when the viscosity is lowered. Excellent balance between properties and high temperature cleanliness.

Claims (13)

A lubricating oil composition containing (A) a lubricating oil base oil and (B) a viscosity index improver, wherein the (A) lubricating oil base oil has a kinematic viscosity of 2.0 to 10.0 mm ² / s at 100 ° C. The lubricating oil composition has a molybdenum content of 100% by mass or less, and the lubricating oil composition has a kinematic viscosity at 100 ° C. of 6.9 mm ² / s or more and less than 9.3 mm ² / s. The lubricating oil having a CCS viscosity of 6.2 Pa · s or less at −35 ° C. and a high temperature high shear viscosity (HTHS viscosity) of 2.6 mPa · s or more at 150 ° C. Composition. The (B) viscosity index improver contains (B1) polymethacrylate having a weight average molecular weight of 100,000 to 400,000, and the amount of the component (B1) is 0.5 to 0.5 to the mass of the entire lubricating oil composition. The lubricating oil composition according to claim 1, wherein the lubricating oil composition is 5.0% by mass. The (B) viscosity index improver contains an α-olefin copolymer having (B2) SSI (shear stability index) of 20 to 30, and the amount of the component (B2) is added to the total mass of the lubricating oil composition. The lubricating oil composition according to claim 1 or 2, wherein the content is 0.5 to 8.0% by mass. The lubricating oil composition further contains (C) a metal cleaning agent, and the content of the (C) metal cleaning agent is 1,000 to 2,500 mass ppm in the lubricating oil composition in terms of metal content. The lubricating oil composition according to any one of claims 1 to 3, which is characterized. The (C) metal cleaning agent contains (C2) a metal cleaning agent having calcium, and the amount of the (C2) metal cleaning agent is 500 to 1,800 mass ppm in the lubricating oil composition in terms of calcium metal. The lubricating oil composition according to claim 4, wherein the lubricating oil composition is characterized by the above. The (C) metal cleaning agent contains a metal cleaning agent having (C1) magnesium, and the amount of the metal cleaning agent having (C1) magnesium is 50 to 800 mass ppm in the lubricating oil composition in terms of magnesium metal. The lubricating oil composition according to claim 4 or 5, characterized in that there is. The lubricating oil composition further contains (D) zinc dialkyldithiophosphate, and the component (D) is zinc dialkyldithiophosphate having (D1) a primary alkyl group and / or (D2) a secondary alkyl group. The lubricating oil composition according to any one of claims 1 to 6, wherein the lubricating oil composition is one or more selected from the above, and the content of the component (D) is 300 to 1,500 mass ppm in terms of the amount of phosphorus. The lubricating oil composition according to claim 7, wherein the lubricating oil composition contains (D2) at least one zinc dialkyldithiophosphate having a secondary alkyl group. The lubricating oil composition according to any one of claims 1 to 8, wherein the molybdenum is derived from a molybdenum-containing friction modifier. The lubricating oil composition according to any one of claims 1 to 9, wherein the lubricating oil composition has an HTTS viscosity of 2.9 mPa · s or less at 150 ° C. The lubricating oil composition according to any one of claims 1 to 10, wherein the (A) lubricating oil base oil contains mineral oil and / or GTL. The lubricating oil composition according to any one of claims 1 to 11, which is used for an internal combustion engine. 12. The lubricating oil composition according to claim 12, which is for a diesel engine.