US20180312776A1

US20180312776A1 - Lubricant composition

Info

Publication number: US20180312776A1
Application number: US15/770,661
Authority: US
Inventors: Mona Ariyama; Hitoshi Komatsubara; Takama YASUDA
Original assignee: JXTG Nippon Oil and Energy Corp
Current assignee: Eneos Corp
Priority date: 2015-10-29
Filing date: 2016-10-28
Publication date: 2018-11-01
Also published as: JPWO2017073748A1; CN108138071B; CN108138071A; WO2017073748A1; JP6657248B2

Abstract

The present invention provides a lubricating oil composition comprising: a lubricating base oil; 1.0% by mass or more and 15.0% by mass or less of a dispersant poly(meth)acrylate compound having the weight average molecular weight of 20000 or more and 200000 or less; 0.05% by mass or more and 6.0% by mass or less of a thiadiazole compound; 1.5% by mass or more and 4.0% by mass or less of a polysulfide compound; and 0.2% by mass or more and 1.5% by mass or less of a friction modifier, based on the total amount of the lubricating oil composition, wherein the mass ratio of the polysulfide compound content to the thiadiazole compound content (polysulfide compound/thiadiazole compound) is 0.4 or more and 50 or less, and the kinematic viscosity at 100° C. of the lubricating oil composition is 7.0 mm²/s or more and 35.0 mm²/s or less.

Description

TECHNICAL FIELD

The present invention relates to a lubricating oil composition.

BACKGROUND ART

Lubricating oil compositions have been used for machines such as internal combustion engines and speed change gears in order to make the operation thereof smooth until now. In lubricating oil compositions, various additives such as antiwear agents, metal-based detergents, ash-free dispersants and antioxidants are mixed into lubricating base oils according to performance requirements (refer to, for example, Patent Literature 1 to 3).

CITATION LIST

Patent Literature

Patent Literature 1: Japanese Unexamined Patent Publication No. 2001-279287
Patent Literature 2: Japanese Unexamined Patent Publication No. 2002-129182
Patent Literature 3: Japanese Unexamined Patent Publication No. H8-302378

SUMMARY OF INVENTION

Technical Problem

An object of the present invention is to provide a lubricating oil composition that is excellent in all of load resistance, fatigue life, shear stability and friction characteristics.

Solution to Problem

The present invention provides a lubricating oil composition comprising: a lubricating base oil; 1.0% by mass or more and 15.0% by mass or less of a dispersant poly(meth)acrylate compound having the weight average molecular weight of 20000 or more and 200000 or less; 0.05% by mass or more and 6.0% by mass or less of a thiadiazole compound; 1.5% by mass or more and 4.0% by mass or less of a polysulfide compound; and 0.2% by mass or more and 1.5% by mass or less of a friction modifier, based on the total amount of the lubricating oil composition, wherein the mass ratio of the polysulfide compound content to the thiadiazole compound content (polysulfide compound/thiadiazole compound) is 0.4 or more and 50 or less, and the kinematic viscosity at 100° C. of the lubricating oil composition is 7.0 mm²/s or more and 35.0 mm²/s or less.
It is preferable that the friction modifier contains at least one selected from the group consisting of primary or secondary amide friction modifiers and primary or secondary amine friction modifiers.
The lubricating oil composition is preferably used as a lubricating oil composition for gear oils.
The lubricating oil composition is preferably used as a lubricating oil composition for final reduction gear oils.

Advantageous Effects of Invention

According to the present invention, a lubricating oil composition that is excellent in all of load resistance, fatigue life, shear stability and friction characteristics can be provided.

DESCRIPTION OF EMBODIMENTS

Embodiments of the present invention will be described in detail hereinafter.
A lubricating oil composition according to this embodiment contains (A) a lubricating base oil, (B) a dispersant poly(meth)acrylate compound, (C) a thiadiazole compound, (D) a polysulfide compound and (E) a friction modifier.
The (A) lubricating base oil (hereinafter called also an “(A) ingredient”) may be a known base oil used for lubricating oils, and may be, for example, a mineral oil base oil, a synthetic base oil or a mixture of both.
The mineral oil base oil includes mineral oil base oils such as paraffinic and naphthenic base oils, normal paraffins and isoparaffins obtained by refining a lubricating oil fraction obtained by atmospheric distillation and vacuum distillation of crude oil through one or suitably combined two or more of refining treatments such as solvent deasphalting, solvent extraction, hydrocracking, solvent dewaxing, contact dewaxing, hydrorefining, sulfuric acid treatment and clay treatment. One of these mineral oil base oils may be used alone, and two or more thereof may be used in combination at any rate.
Preferable mineral oil base oils include the following base oils:
(1) a distilled oil obtained by the atmospheric distillation of a paraffinic crude oil and/or a mixed-base crude oil;
(2) a whole vacuum gas oil (WVGO) of an atmospheric distillation residual oil of a paraffinic crude oil and/or a mixed-base crude oil;
(3) wax obtained by a process of dewaxing a lubricating oil and/or Fischer Tropsch wax produced by a GTL process and the like;
(4) a mild hydrocracking treatment oil (MHC) of one or a blended oil of two or more selected from the above (1) to (3);
(5) a blended oil of two or more oils selected from the above (1) to (4);
(6) a deasphalted oil (DAO) of the above (1), (2), (3), (4), or (5);
(7) a mild hydrocracking treatment oil (MHC) of the above (6); and
(8) a lubricating oil obtained by using a blended oil of two or more oils selected from the above (1) to (7) or the like as a raw material oil, refining this raw material oil and/or a lubricating oil fraction collected therefrom in a usual refining method and collecting a lubricating oil fraction.
Here, the usual refining method is not limited particularly, and may be any refining method used at the time of production of base oils. Examples of the usual refining method include the following refining methods:
(a) hydrorefining such as hydrocracking or hydrofinishing;
(b) solvent refining such as furfural solvent extraction;
(c) dewaxing such as solvent dewaxing or contact dewaxing;
(d) clay refining by acid clay, activated clay or the like;
(e) chemical (acid or alkali) refining such as sulfuric acid treatment or sodium hydroxide treatment.
One of these refining methods may be adopted alone, and two or more thereof may be adopted in any combination and any order.
The synthetic base oils include poly-α-olefins or hydrides thereof; isobutene oligomers or hydrides thereof; isoparaffins; alkylbenzenes; alkylnaphthalenes; diesters (such as ditridecyl glutarate, di-2-ethylhexyl adipate, di-2-ethylhexyl azelate, di-isodecyl adipate, ditridecyl adipate, and di-2-ethylhexyl sebacate); polyol esters (such as trimethylolpropane caprylate, trimethylolpropane pelargonate, pentaerythritol 2-ethylhexanoate, and pentaerythritol pelargonate); polyoxyalkylene glycols; dialkyldiphenyl ethers; and polyphenyl ether, and poly-α-olefins are preferable particularly. Examples of the poly-α-olefins include oligomers or co-oligomers of α-olefins (such as 1-octene oligomers, decene oligomers, and ethylene-propylene co-oligomers) having 2 or more and 32 or less carbon atoms, and preferably 6 or more and 16 or less, and hydrides thereof. One of these synthetic base oils may be used alone, and two or more thereof may be used in combination at any rate.
The kinematic viscosity at 40° C. of a lubricating base oil is preferably 20 mm²/s or more, more preferably 50 mm²/s or more, and still more preferably 90 mm²/s or more. When the kinematic viscosity at 40° C. of a lubricating base oil is 20 mm²/s or more, oil film formation becomes satisfactory, and it becomes easier to obtain a lubricating oil composition that is excellent in lubricity and the evaporation loss of which under a high temperature condition is lower. The kinematic viscosity at 40° C. of a lubricating base oil is preferably 180 mm²/s or less, more preferably 140 mm²/s or less, and still more preferably 130 mm²/s or less. When the kinematic viscosity at 40° C. of a lubricating base oil is 180 mm²/s or less, the fluid resistance becomes lower, and therefore, it becomes easier to obtain a lubricating oil composition the rotational resistance of which is lower.
The kinematic viscosity at 100° C. of a lubricating base oil is preferably 3.0 mm²/s or more, more preferably 5.0 mm²/s or more, and still more preferably 10.0 mm²/s or more. When the kinematic viscosity at 100° C. of a lubricating base oil is 3.0 mm²/s or more, oil film formation becomes satisfactory, and it becomes easier to obtain a lubricating oil composition that is excellent in lubricity and the evaporation loss of which under a high temperature condition is lower. The kinematic viscosity at 100° C. of a lubricating base oil is preferably 25 mm²/s or less, more preferably 18 mm²/s or less, and still more preferably 15 mm²/s or less. When the kinematic viscosity at 100° C. of a lubricating base oil is 25 mm²/s or less, the fluid resistance becomes lower, and therefore, it becomes easier to obtain a lubricating oil composition the rotational resistance of which is lower.
The viscosity index of a lubricating base oil is preferably 60 or more, more preferably 80 or more, and still more preferably 90 or more. When the viscosity index is 60 or more, it becomes easier to obtain a lubricating oil composition exhibiting better viscosity characteristics in the range from low temperatures to high temperatures.
The kinematic viscosity and the viscosity index in the present invention mean a kinematic viscosity and a viscosity index measured in accordance with JIS K2283: 2000, respectively.
The sulfur content in a lubricating base oil may be 5000 ppm by mass or less, 4500 ppm by mass or less, or 4000 ppm by mass or less on the basis of the total amount of the lubricating base oil. The sulfur content in a lubricating base oil can be measured by an ICP elementary analysis method.
The content of the (A) ingredient may be, for example, 70% by mass or more, 80% by mass or more, or 85% by mass or more on the basis of the total amount of the lubricating oil composition. The content of the (A) ingredient may be, for example, 95% by mass or less, 93% by mass or less, or 90% by mass or less on the basis of the total amount of the lubricating oil composition.
The (B) dispersant poly(meth)acrylate compound (hereinafter called also a “(B) ingredient”) contains a poly(meth)acrylate compound having a dispersant group. The dispersant group is preferably a nitrogen-containing dispersant group, and more preferably a dimethylamino group.
The (B) ingredient preferably contains a poly(meth)acrylate compound having at least one structural unit selected from a structural unit represented by the following formula (1) and a structural unit represented by the following formula (2).
[In the formula (1), R¹represents a hydrogen atom or a methyl group, R²represents an alkylene group the carbon number of which is 1 to 18, E¹represents an amine residue or a heterocyclic residue having 1 to 2 nitrogen atoms and 0 to 2 oxygen atoms, and in represents 0 or 1.]
[In the formula (2), R³represents a hydrogen atom or a hydrocarbon group, and E²represents an amine residue or a heterocyclic residue having 1 to 2 nitrogen atoms and 0 to 2 oxygen atoms.]
Examples of the alkylene group the carbon number of which is 1 to 18 and that is represented by R²include an ethylene group, a propylene group, a butylene group, a pentylene group, a hexylene group, a heptylene group, an octylene group, a nonylene group, a decylene group, an undecylene group, a dodecylene group, a tridecylene group, a tetradecylene group, a pentadecylene group, a hexadecylene group, a heptadecylene group, and an octadecylene group. These alkylene groups may be linear or branched.
The hydrocarbon group represented by R³may be, for example, a linear or branched hydrocarbon group the carbon number of which is 1 to 12.
Examples of the groups represented by E¹and E²each include a dimethylamino group, a diethylamino group, a dipropylamino group, a dibutylamino group, an anilino group, a toluidino group, a xylidino group, an acetylamino group, a benzoylamino group, a morpholino group, a pyrrolyl group, a pyrrolino group, a pyridyl group, a methylpyridyl group, a pyrrolidinyl group, a piperidinyl group, a quinonyl group, a pyrrolidonyl group, a pyrrolidono group, an imidazolino group, and a pyrazino group.
The weight average molecular weight of a dispersant poly(meth)acrylate is preferably 20000 or more, more preferably 30000 or more, and still more preferably 40000 or more in view of an excellent fatigue life. The weight average molecular weight of a dispersant poly(meth)acrylate is preferably 200000 or less, more preferably 170000 or less, still more preferably 110000 or less, and particularly preferably 50000 or less in view of excellent shear stability. The weight average molecular weight of a dispersant poly(meth)acrylate is 20000 or more and 200000 or less; preferably 20000 or more and 170000 or less; 20000 or more and 110000 or less; 20000 or more and 50000 or less; 30000 or more and 200000 or less; 30000 or more and 170000 or less; 30000 or more and 110000 or less; 30000 or more and 50000 or less; 40000 or more and 200000 or less; 40000 or more and 170000 or less; 40000 or more and 110000 or less; or 40000 or more and 50000 or less in view of compatibility between fatigue life and shear stability. The weight average molecular weight in the present invention means a weight average molecular weight measured by GPC analysis (a value in terms of polystyrene (standard sample)).
The content of the (B) ingredient is preferably 1.0% by mass or more, more preferably 2.0% by mass or more, and still more preferably 2.5% by mass or more on the basis of the total amount of the lubricating oil composition in view of an excellent fatigue life. The content of the (B) ingredient is preferably 15.0% by mass or less, more preferably 9.0% by mass or less, and preferably 5.0% by mass or less on the basis of the total amount of the lubricating oil composition in view of excellent shear stability. The content of the (B) ingredient is 1.0% by mass or more and 15.0% by mass or less, and preferably 1.0% by mass or more and 9.0% by mass or less; 1.0% by mass or more and 5.0% by mass or less; 2.0% by mass or more and 15.0% by mass or less; 2.0% by mass or more and 9.0% by mass or less; 2.0% by mass or more and 5.0% by mass or less; 2.5% by mass or more and 15.0% by mass or less; 2.5% by mass or more and 9.0% by mass or less; or 2.5% by mass or more and 5.0% by mass or less on the basis of the total amount of the lubricating oil composition in view of compatibility between fatigue life and shear stability.
The (C) thiadiazole compound (hereinafter called also a “(C) ingredient”) may be a known thiadiazole compound, and may be, for example, a 1,3,4-thiadiazole compound represented by the following formula (3), a 1,2,4-thiadiazole compound represented by the following formula (4), or a 1,2,3-thiadiazole compound represented by the following formula (5).
where R⁴, R⁵, R⁶, R⁷, R⁸and R⁹each independently represent a hydrogen atom or a hydrocarbon group the carbon number of which is 1 to 20, and a, b, c, d, e and f each independently represent an integer of 0 to 8.
Specific examples of such a thiadiazole compound include 2,5-bis(n-hexyldithio)-1,3,4-thiadiazole; 2,5-bis(n-octyldithio)-1,3,4-thiadiazole; 2,5-bis(n-nonyldithio)-1,3,4-thiadiazole; 2,5-bis(1,1,3,3-tetramethylbutyldithio)-1,3,4-thiadiazole; 3,5-bis(n-hexyldithio)-1,2,4-thiadiazole; 3,5-bis(n-octyldithio)-1,2,4-thiadiazole; 3,5-bis(n-nonyldithio)-1,2,4-thiadiazole; 3,5-bis(1,1,3,3-tetramethylbutyldithio)-1,2,4-thiadiazole; 4,5-bis(n-hexyldithio)-1,2,3-thiadiazole; 4,5-bis(n-octyldithio)-1,2,3-thiadiazole; 4,5-bis(n-nonyldithio)-1,2,3-thiadiazole; and 4,5-bis(1,1,3,3-tetramethylbutyldithio)-1,2,3-thiadiazole.
The content of the (C) ingredient is preferably 0.05% by mass or more, more preferably 0.2% by mass or more, still more preferably 1.0% by mass or more, and particularly preferably 1.5% by mass or more on the basis of the total amount of the lubricating oil composition in view of excellent load resistance. The content of the (C) ingredient is preferably 6.0% by mass or less, more preferably 4.5% by mass or less, and still more preferably 3.0% by mass or less on the basis of the total amount of the lubricating oil composition in view of an excellent fatigue life. The content of the (C) ingredient is 0.05% by mass or more and 6.0% by mass or less; preferably 0.05% by mass or more and 4.5% by mass or less; 0.05% by mass or more and 3.0% by mass or less; 0.2% by mass or more and 6.0% by mass or less; 0.2% by mass or more and 4.5% by mass or less; 0.2% by mass or more and 3.0% by mass or less; 1.0% by mass or more and 6.0% by mass or less; 1.0% by mass or more and 4.5% by mass or less; 1.0% by mass or more and 3.0% by mass or less; 1.5% by mass or more and 6.0% by mass or less; 1.5% by mass or more and 4.5% by mass or less; or 1.5% by mass or more and 3.0% by mass or less on the basis of the total amount of the lubricating oil composition in view of compatibility between load resistance and fatigue life.
The (D) polysulfide compound (hereinafter called also a “(D) ingredient”) may be a known polysulfide compound, and may be, for example, a compound represented by the following formula (6).
R¹⁰—S_x—R¹¹ (6)
In the formula (6), R¹⁰and R¹¹each independently represents a linear or branched alkyl group the carbon number of which is 3 to 20, an aryl group the carbon number of which is 6 to 20, an alkaryl group the carbon number of which is 6 to 20, or an aralkyl group the carbon number which is 6 to 20, and x represents an integer of 2 to 6, and preferably an integer of 2 to 5.
The content of the (D) ingredient is preferably 1.5% by mass or more, more preferably 1.8% by mass or more, and still more preferably 2.0% by mass or more on the basis of the total amount of the lubricating oil composition in view of excellent extreme pressure characteristics. The content of the (D) ingredient is preferably 4.0% by mass or less, more preferably 3.0% by mass or less, still more preferably 2.5% by mass or less, and particularly preferably 2.2% by mass or less on the basis of the total amount of the lubricating oil composition in view of an excellent fatigue life. The content of a (D) ingredient is 1.5% by mass or more and 4.0% by mass or less; preferably 1.5% by mass or more and 3.0% by mass or less; 1.5% by mass or more and 2.5% by mass or less; 1.8% by mass or more and 4.0% by mass or less; 1.8% by mass or more and 2.5% by mass or less; 1.8% by mass or more and 2.2% by mass or less; 2.0% by mass or more and 4.0% by mass or less; 2.0% by mass or more and 2.5% by mass or less; or 2.0% by mass or more and 2.2% by mass or less on the basis of the total amount of the lubricating oil composition in view of compatibility between extreme pressure characteristics and fatigue life.
The (E) friction modifier (hereinafter called also an “(E) ingredient”) may be a known friction modifier, and may be, for example, an amine, amide, imide, fatty acid ester, fatty acid, aliphatic alcohol, or aliphatic ether friction modifier. The (E) ingredient preferably contains at least one friction modifier selected from the group consisting of primary or secondary amine friction modifiers and primary or secondary amide friction modifiers.
Examples of the primary or secondary amine friction modifier include alkylamines such as methylamine, ethylamine, propylamine, butylamine, pentylamine, hexylamine, heptylamine, octylamine, nonylamine, decylamine, undecylamine, dodecylamine (laurylamine), tridecylamine, tetradecylamine, pentadecylamine, hexadecylamine, heptadecylamine, octadecylamine (stearylamine), docosylamine (behenylamine), dimethylamine, diethylamine, dipropylamine, dibutylamine, dipentylamine, dihexylamine, diheptylamine, dioctylamine, dinonylamine, didecylamine, diundecylamine, didodecylamine, ditridecyl amine, ditetradecylamine, dipentadecylamine, dihexadecylamine, diheptadecylamine, dioctadecylamine, methylethyl amine, methylpropylamine, methylbutyl amine, ethylpropylamine, ethylbutylamine, and propylbutylamine that have alkyl groups with 1 to 30 carbon atoms (these alkyl groups may be linear or branched); alkenylamines such as ethenylamine, propenylamine, butenylamine, octenylamine, and oleylamine that have alkenyl groups with 2 to 30 carbon atoms (these alkenyl groups may be linear or branched); alicyclic amines such as cyclohexylamine; and alkylenediamines such as methylenediamine, ethylenediamine, propylenediamine, and butylenediamine that have alkylene groups with 1 to 30 carbon atoms. Among these, alkylamines and alkenyl amines are preferable. The numbers of carbon atoms of the alkyl groups of alkylamines are preferably 4 to 28, and more preferably 6 to 25. The numbers of carbon atoms of the alkenyl group of alkenyl amines are preferably 4 to 28, and more preferably 6 to 25.
Examples of the primary or secondary amide friction modifier include saturated fatty acid amides such as ethanoic acid amide, propanoic acid amide, butanoic acid amide, octanoic acid amide, decanoic acid amide, dodecanoic acid amide, hexadecanoic acid amide, octadecanoic acid amide, docosanoic acid amide that have alkyl groups with 1 to 30 carbon atoms (these alkyl groups may be linear or branched); unsaturated fatty acid amides such as oleic acid amide and erucic acid amide that have alkenyl groups with 2 to 30 carbon atoms (these alkenyl groups may be linear or branched). The numbers of carbon atoms of the alkyl groups of saturated fatty acid amides are preferably 4 to 28, and more preferably 6 to 25. The numbers of carbon atoms of the alkenyl groups of unsaturated fatty acid amides are preferably 4 to 28, more preferably 6 to 25.
The content of the (E) ingredient is preferably 0.2% by mass or more, more preferably 0.5% by mass or more, and still more preferably 0.7% by mass or more on the basis of the total amount of the lubricating oil composition in view of excellent friction characteristics. The content of the (E) ingredient is preferably 1.5% by mass or less, more preferably 1.2% by mass or less, and still more preferably 0.9% by mass or less on the basis of the total amount of the lubricating oil composition in view of excellent oxidation stability. The content of the (E) ingredient is 0.2% by mass or more and 1.5% by mass or less; and preferably 0.2% by mass or more and 1.2% by mass or less; 0.2% by mass or more and 0.9% by mass or less; 0.5% by mass or more and 1.5% by mass or less; 0.5% by mass or more and 1.2% by mass or less; 0.5% by mass or more and 0.9% by mass or less; 0.7% by mass or more and 1.5% by mass or less; 0.7% by mass or more and 1.2% by mass or less; or 0.7% by mass or more and 0.9% by mass or less on the basis of the total amount of the lubricating oil composition in view of compatibility between friction characteristics and oxidation stability.
In the lubricating oil composition, the mass ratio of the content of the (D) polysulfide compound to the content of the (C) thiadiazole compound ((D) polysulfide compound/(C) thiadiazole compound) is 0.4 or more and 50 or less, more preferably 0.5 or more and 30 or less, still more preferably 1.0 or more and 15 or less, and particularly preferably 1.0 or more and 10 or less in view of an excellent fatigue life. The mass ratio ((D) ingredient/(C) ingredient) may be 0.4 or more, 0.5 or more, and 1.0 or more, and may be 50 or less, 30 or less, 15 or less, and 10 or less.
In addition to the above (A) to (E) ingredients, the lubricating oil composition may further contain other additives if needed. Examples of the other additives include an extreme pressure agent, a viscosity modifier, a metal-based detergent, an ash-free dispersant, an antioxidant, a corrosion inhibitor, an antirust, a demulsifier, a metal deactivator, and a defoaming agent.
The extreme pressure agent includes phosphorus-based extreme pressure agents such as phosphites and phosphates as well as amine salts, metal salts and derivatives thereof; and sulfur-based extreme pressure agents such as dithiocarbamate, zinc dithiocarbamate, molybdenum dithiocarbamate (MoDTC), olefin sulfide, and sulfurized oil and fat.
Examples of the viscosity modifier include non-dispersant poly (meth)acrylate viscosity modifiers; styrene-maleic anhydride ester copolymer viscosity modifiers; non-dispersant or dispersant ethylene-α-olefin copolymers or hydrides thereof; polyisobutylene or the hydride thereof; styrene-diene hydrogenated copolymers; and polyalkylstyrenes.
The metal-based detergent includes salicylate detergents, phenate detergents, sulfonate detergents. These metal-based detergents may be any of a normal salt, a basic salt and a perbasic salt with an alkali metal or an alkaline earth metal.
The ash-free dispersant includes nitrogen-containing compounds such as succinimide, benzylamine, polyamines, and Mannich bases that have alkenyl groups or alkyl groups derived from polyolefins; and boron-modified nitrogen-containing compounds (boron-based ash-free dispersants) such as boron-modified succinimide obtained by modifying these nitrogen-containing compounds with boron compounds such as boric acid and borates.
The antioxidant includes ash-free antioxidants such as phenol and amine antioxidants; and metal-based antioxidants such as copper-based and molybdenum-based antioxidants. Specific examples of the phenol ash-free antioxidants include 4,4′-methylene-bis-(2,6-di-tert-butylphenol), 4,4′-bis(2,6-di-tert-butylphenol), and specific examples of amine ash-free antioxidants include phenyl-α-naphthylamine, alkylphenyl-α-naphthylamines, dialkyldiphenylamines, and diphenylamine.
Examples of the corrosion inhibitor include benzotriazole, tolyltriazole and imidazole compounds.
Examples of the antirust include alkenyl succinates, polyhydric alcohol esters, petroleum sulfonates, alkylbenzene sulfonates, and dinonylnaphthalene sulfonate.
Examples of the demulsifier include polyalkylene glycol-based non-ionic surfactants such as polyoxyethylene alkyl ethers, polyoxyethylene alkyl phenyl ethers, and polyoxyethylene alkyl naphthyl ethers.
Examples of the metal deactivator include imidazoline, pyrimidine derivatives, and benzotriazol or derivatives thereof.
Examples of the defoaming agent include silicone oil, alkenyl succinic acid derivatives, the esters of polyhydroxy aliphatic alcohols and long-chain fatty acids, and the ester of methyl salicylate and o-hydroxybenzyl alcohol the kinematic viscosity of which at 25° C. is 1000 mm²/s or more and 100000 mm²/s or less.
The content of the other additives may be 0.01 to 20% by mass on the basis of the total amount of the lubricating oil composition.
The kinematic viscosity at 40° C. of the lubricating oil composition is preferably 70 mm²/s or more, more preferably 100 mm²/s more, and still more preferably 120 mm²/s or more. Since the kinematic viscosity at 40° C. is 60 mm²/s or more, the lubricating oil composition tends to be excellent in oil film retentivity and evaporativity on lubricated portions. The kinematic viscosity at 40° C. of the lubricating oil composition is preferably 250 mm²/s or less, more preferably 230 mm²/s or less, and still more preferably 210 mm²/s or less. Since the kinematic viscosity at 40° C. is 260 mm²/s or less, the lubricating oil composition tends to be excellent in cold flow property and fuel efficiency.
The kinematic viscosity at 100° C. of the lubricating oil composition is preferably 7.0 mm²/s or more, more preferably 10.0 mm²/s or more, and still more preferably 13.0 mm²/s or more. Since the kinematic viscosity at 100° C. is 7.0 mm²/s or more, the lubricating oil composition is excellent in load resistance and fatigue life. The kinematic viscosity at 100° C. of the lubricating oil composition is preferably 35.0 mm²/s or less, more preferably 25.0 mm²/s or less, and still more preferably 20.0 mm²/s or less. Since the kinematic viscosity at 100° C. is 35.0 mm²/s or less, the lubricating oil composition tends to be excellent in cold flow property and fuel efficiency. In view of excellence in all of load resistance, fatigue life, cold flow property and fuel efficiency, the kinematic viscosity at 100° C. of the lubricating oil composition is 7.0 mm²/s or more and 35.0 mm²/s or less; preferably 7.0 mm²/s or more and 25.0 mm²/s or less; 7.0 mm²/s or more and 20.0 mm²/s or less; 10.0 mm²/s or more and 35.0 mm²/s or less; 10.0 mm²/s or more and 25.0 mm²/s or less; 10.0 mm²/s or more and 20.0 mm²/s or less; 13.0 mm²/s or more and 35.0 mm²/s or less; 13.0 mm²/s or more and 25.0 mm²/s or less; or 13.0 mm²/s or more and 20.0 mm²/s or less.
The content of a sulfur element (C_S) in a lubricating oil composition may be, for example, 10000 ppm by mass or more, and may be 31000 ppm by mass or less on the basis of the total amount of the lubricating oil composition. A sulfur element in a lubricating oil composition is derived from a sulfur element contained in the lubricating base oil and the additives such as the (C) and (D) ingredients.
The content of a phosphorus element (C_P) in the lubricating oil composition may be, for example, 700 ppm by mass or more, and may be 2000 ppm by mass or less on the basis of the total amount of a lubricating oil composition. A phosphorus element in a lubricating oil composition is derived from a phosphorus element contained in additives such as a phosphorus-based extreme pressure agent.
The content of a boron element (C_B) in the lubricating oil composition may be, for example, 30 ppm by mass or more, and may be 200 ppm by mass or less on the basis of the total amount of a lubricating oil composition. A boron element in a lubricating oil composition is derived from a boron element contained in additives such as a boron-based ash-free dispersant.
In a lubricating oil composition, the respective contents of a sulfur element, a phosphorus element and a boron element (ppm by mass; on the basis the total amount of the lubricating oil composition) preferably satisfy the following expression (7) in view of more excellent load resistance and a more excellent fatigue life.
0.05≤C_S/(C_P×C_B)≤0.50 (7)
C_S/(C_P×C_B) is preferably 0.05 or more, more preferably 0.07 or more, still more preferably 0.12 or more, and particularly preferably 0.25 or more in view of more excellent load resistance. C_S/(C_P×C_B) is preferably 0.50 or less, more preferably 0.45 or less, still more preferably 0.40 or less, and particularly preferably 0.35 or less in view of a more excellent fatigue life. The respective contents of a sulfur element, a phosphorus element and a boron element can be measured by an ICP elementary analysis method.
A lubricating oil composition according to this embodiment can be used for a usual use of lubricating oils and preferably used as a lubricating oil composition for gear oils. More specifically, the lubricating oil composition is preferably applied to manual transmissions for cars, automatic transmissions, continuously variable transmission or final reduction gears, or industrial gear systems. The lubricating oil composition is particularly preferably used as a lubricating oil composition for final reduction gear oils.

EXAMPLES

Although the present invention will be described more specifically hereinafter on the basis of Examples, the present invention is not limited to the following Examples.
Lubricating oil compositions were prepared by using lubricating base oils and additives shown below. The composition of the lubricating oil compositions is shown in Tables 1 to 5.
[Lubricating Base Oil]
A-1: a solvent-refined mineral oil (Gr I, kinematic viscosity at 40° C.: 22.7 mm²/s, kinematic viscosity at 100° C.: 4.4 mm²/s, viscosity index: 102, sulfur content: 0.14% by mass)
A-2: a solvent-refined mineral oil (Gr I, kinematic viscosity at 40° C.: 478.3 mm²/s, kinematic viscosity at 100° C.: 31.6 mm²/s, viscosity index: 97, sulfur content: 0.48% by mass)
A-3: a solvent-refined mineral oil (Gr I, kinematic viscosity at 40° C.: 95.1 mm²/s, kinematic viscosity at 100° C.: 10.9 mm²/s, viscosity index: 98, sulfur content: 0.58% by mass)
A-4: a hydrorefined mineral oil (Gr III, kinematic viscosity at 40° C.: 46.71 mm²/s, kinematic viscosity at 100° C.: 7.595 mm²/s, viscosity index: 129, sulfur content: <10 ppm by mass)
A-5: a hydrorefined mineral oil (Gr III, kinematic viscosity at 40° C.: 8.73 mm²/s, kinematic viscosity at 100° C.: 2.435 mm²/s, viscosity index: 98, sulfur content: <10 ppm by mass)
A-6: a poly-α-olefin (Gr IV, kinematic viscosity at 40° C.: 405 mm²/s, kinematic viscosity at 100° C.: 50 mm²/s, viscosity index: 187, sulfur content: <10 ppm by mass)

[Additives]

B-1: a dispersant poly(meth)acrylate (weight average molecular weight: 40000)
B-2: a dispersant poly(meth)acrylate (weight average molecular weight: 60000)
B-3: a dispersant poly(meth)acrylate (weight average molecular weight: 150000)
b-1: a dispersant poly(meth)acrylate (weight average molecular weight: 10000)
b-2: a dispersant poly(meth)acrylate (weight average molecular weight: 250000)
b-3: a non-dispersant poly(meth)acrylate (weight average molecular weight: 40000)
b-4: a non-dispersant poly(meth)acrylate (weight average molecular weight: 150000)
C-1: 2,5-bis(alkyldithio)-1,3,4-thiadiazole (sulfur element content: 36.0% by mass)
C-2: 2,5-bis(alkyldithio)-1,3,4-thiadiazole (sulfur element content: 34.7% by mass)
D-1: polysulfide (sulfur element content: 45.8% by mass)
E-1: oleylamine
E-2: 2-ethylhexylamine
E-3: distearylamine
E-4: oleic acid amide
F-1: di-n-butyl phosphite (phosphorus element content: 15.5% by mass)
G-1: 10% by mass of a boron-based dispersant, 0.1% by mass of an amine antioxidant, 15% by mass of a phosphoric ester, 0.5% by mass of a defoaming agent, and an additive package containing 10% by mass of a diluent oil
G-2: 15% by mass of a boron-based dispersant, 0.1% by mass of an amine antioxidant, 17% by mass of a phosphoric ester, 0.5% by mass of a defoaming agent, and an additive package containing 10% by mass of a diluent oil
G-3: 0.1% by a mass of boron-based dispersant, 0.1% by mass of an amine antioxidant, 10% by mass of a phosphoric ester, 0.5% by mass of a defoaming agent, and an additive package containing 5% by mass of a diluent oil
For the lubricating oil compositions, evaluation tests shown below were conducted. Results are illustrated in Tables 1 to 5.
[Load Resistance Test]
For the lubricating oil compositions, weld loads (WL) at 1800 rpm were measured by using a high-speed four ball tester on the basis of ASTM D2596. A heavier weld load (for example, 3089 N or more) means a higher load resistance in the test.
[Fatigue Life Test]
The fatigue life of gears until pitching occurs under the following conditions was evaluated by using a unisteel rolling fatigue testing machine. A longer fatigue life of the gears (for example, 1000 minutes or more) means a longer fatigue life of the lubricating oil composition.
Specimen: thrust needle
Contact pressure: 2 GPa
Oil temperature: 120° C.
Number of revolutions: 1410 rpm
[Shear Stability Test]
A sonic test was conducted under the following conditions on the basis of JPI-5S-29-88, the kinematic viscosity at 100° C. before and after the sonic test was measured, and a decrease in the viscosity was calculated therefrom. A smaller decrease in viscosity (for example, 8% or less) means a higher shear stability in the test.
Frequency: 10 kHz
Amplitude: 28 μM
Exposure time: 1 hour
[Coefficient of Friction Test]
The coefficients of friction between metals were evaluated under the following conditions by using an LFW-1 testing machine. A smaller coefficient of friction between metals (for example, 0.15 or less) means a better friction characteristic.
Specimen: block H60, ring S10
Load: 3113 N
Sliding velocity: 0.5 m/s
Oil temperature: 90° C.

TABLE 1

	Example 1	Example 2	Example 3	Example 4

Base oil composition
(% by mass on the basis of the total
amount of base oil)
A-1	(38)	(38)	(38)	(38)
A-2	(62)	(62)	(62)	(62)
Base oil kinematic viscosity
(mm²/s)
40° C.	118.1	118.1	118.1	118.1
100° C.	12.7	12.7	12.7	12.7
Sulfur content in base oil	3508	3508	3508	3508
(ppm by mass)
Lubricating oil composition
(% by mass on the basis of the total
amount of lubricating oil)
Base oil	Balance	Balance	Balance	Balance
B-1	3.0	—	—	1.0
B-2	—	3.0	—	—
B-3	—		3.0	—
C-1	1.5	1.5	1.5	1.5
C-2	—	—	—	—
D-1	2.0	2.0	2.0	2.0
E-1	0.80	0.80	0.80	0.80
G-1	5.0	5.0	5.0	5.0
D ingredient content/C ingredient	1.4	1.4	1.4	1.4
content
Sulfur content in additives	14524	14524	14524	14524
(ppm by mass)
Properties of lubricating oil
Kinematic viscosity (mm²/s)
40° C.	144.3	148.5	167.3	127.7
100° C.	15.6	15.9	17.7	14.2
Viscosity index	111	111	116	110
Elementary analysis (ppm by mass)
P	1100	1100	1100	1100
S	18032	18032	18032	18032
B	55	55	55	55
Evaluation test results
Load resistance (N)	3923	3923	3923	3923
Fatigue life (min)	1578	1590	1628	1228
Shear stability
Kinematic viscosity after shear	15.5	15.7	17.0	14.1
Decrease in viscosity (%)	0.7	1.6	4.2	0.6
Friction characteristics	0.09	0.09	0.09	0.09

	Example 5	Example 6	Example 7	Example 8

Base oil composition
(% by mass on the basis of the total
amount of base oil)
A-1	(38)	(38)	(38)	(38)
A-2	(62)	(62)	(62)	(62)
Base oil kinematic viscosity
(mm²/s)
40° C.	118.1	118.1	118.1	118.1
100° C.	12.7	12.7	12.7	12.7
Sulfur content in base oil	3508	3508	3508	3508
(ppm by mass)
Lubricating oil composition
(% by mass on the basis of the total
amount of lubricating oil)
Base oil	Balance	Balance	Balance	Balance
B-1	13.0	3.0	3.0	3.0
B-2	—	—	—	—
B-3	—	—	—	—
C-1	1.5	2.4	—	1.5
C-2	—	—	1.5	—
D-1	2.0	2.0	2.0	2.0
E-1	0.80	0.80	0.80	0.30
G-1	5.0	5.0	5.0	5.0
D ingredient content/C ingredient	1.4	0.8	1.4	1.4
content
Sulfur content in additives	14524	17944	14331	14524
(ppm by mass)
Properties of lubricating oil
Kinematic viscosity (mm²/s)
40° C.	201.4	144.3	144.3	144.3
100° C.	20.0	15.6	15.6	15.6
Viscosity index	115	111	111	111
Elementary analysis (ppm by mass)
P	1100	1100	1100	1100
S	18032	25052	17839	18032
B	55	55	55	55
Evaluation test results
Load resistance (N)	3923	4903	3923	3923
Fatigue life (min)	2198	1432	1498	16852
Shear stability
Kinematic viscosity after shear	19.4	15.5	15.5	15.5
Decrease in viscosity (%)	3.1	0.7	0.7	0.7
Friction characteristics	0.09	0.09	0.09	0.12

TABLE 2

	Example 9	Example 10	Example 11	Example 12

Base oil composition
(% by mass on the basis of the total
amount of base oil)
A-1	(38)	(38)	(38)	(38)
A-2	(62)	(62)	(62)	(62)
Base oil kinematic viscosity
(mm²/s)
40° C.	118.1	118.1	118.1	118.1
100° C.	12.7	12.7	12.7	12.7
Sulfur content in base oil	3508	3508	3508	3508
(ppm by mass)
Lubricating oil composition
(% by mass on the basis of the total
amount of lubricating oil)
Base oil	Balance	Balance	Balance	Balance
B-1	3.0	3.0	3.0	3.0
C-1	1.5	1.5	1.5	1.5
D-1	2.0	2.0	2.0	2.0
E-1	1.00	—	—	—
E-2	—	0.80	—	—
E-3	—	—	0.80	—
E-4	—	—	—	0.08
F-1	—	—	—	—
G-1	5.0	5.0	5.0	5.0
G-2	—	—	—	—
G-3	—	—	—	—
D ingredient content/C ingredient	1.4	1.4	1.4	1.4
content
Sulfur content in additives	14524	14524	14524	14524
(ppm by mass)
Properties of lubricating oil
Kinematic viscosity (mm²/s)
40° C.	144.3	144.3	144.3	144.3
100° C.	15.6	15.6	15.6	15.6
Viscosity index	111	111	111	111
Elementary analysis (ppm by mass)
P	1100	1100	1100	1100
S	18032	18032	18032	18032
B	55	55	55	55
Evaluation test results
Load resistance (N)	3923	3923	3923	3923
Fatigue life (min)	1424	1592	1569	1580
Shear stability
Kinematic viscosity after shear	15.5	15.5	15.5	15.5
Decrease in viscosity (%)	0.7	0.7	0.7	0.7
Friction characteristics	0.08	0.10	0.10	0.10

	Example 13	Example 14	Example 15	Example 16

Base oil composition
(% by mass on the basis of the total
amount of base oil)
A-1	(38)	(38)	(38)	(38)
A-2	(62)	(62)	(62)	(62)
Base oil kinematic viscosity
(mm²/s)
40° C.	118.1	118.1	118.1	118.1
100° C.	12.7	12.7	12.7	12.7
Sulfur content in base oil	3508	3508	3508	3508
(ppm by mass)
Lubricating oil composition
(% by mass on the basis of the total
amount of lubricating oil)
Base oil	Balance	Balance	Balance	Balance
B-1	3.0	3.0	3.0	3.0
C-1	1.5	0.2	0.1	0.1
D-1	2.0	2.7	3.5	3.5
E-1	0.80	0.80	0.80	0.80
E-2	—	—	—	—
E-3	0.09	—	—	—
E-4	—	—	—	—
F-1	—	—	—	0.65
G-1	5.0	—	—	—
G-2	—	7.0	—	—
G-3	—	—	7.0	7.0
D ingredient content/C ingredient	1.4	14.9	50	50
content
Sulfur content in additives	14524	12945	16282	16282
(ppm by mass)
Properties of lubricating oil
Kinematic viscosity (mm²/s)
40° C.	144.3	144.5	144.6	144.9
100° C.	15.6	15.8	15.8	15.7
Viscosity index	111	111	113	112
Elementary analysis (ppm by mass)
P	1100	1400	890	1600
S	18032	16453	19790	19790
B	55	150	170	170
Evaluation test results
Load resistance (N)	3923	3089	3923	3089
Fatigue life (min)	1555	1572	1489	1679
Shear stability
Kinematic viscosity after shear	15.5	15.7	15.7	15.6
Decrease in viscosity (%)	0.7	0.7	0.8	0.8
Friction characteristics	0.08	0.09	0.09	0.09

TABLE 3

	Example 17	Example 18	Example 19	Example 20

Base oil composition
(% by mass on the basis of the total
amount of base oil)
A-1	(5)	(28)	(38)	(38)
A-2	(80)	(52)	(62)	(62)
A-3	(15)	—	—	—
A-4	—	(20)	—	—
A-6	—	—	—	—
Base oil kinematic viscosity
(mm²/s)
40° C.	106.6	104.1	118.1	118.1
100° C.	11.7	12.0	12.7	12.7
Sulfur content in base oil	4780	2888	3508	3508
(ppm by mass)
Lubricating oil composition
(% by mass on the basis of the total
amount of lubricating oil)
Base oil	Balance	Balance	Balance	Balance
B-1	3.0	3.0	3.0	3.0
C-1	1.5	1.5	3.4	5.4
D-1	2.3	2.0	2.0	2.0
E-1	0.80	0.80	0.80	0.80
G-1	5.0	5.0	5.0	5.0
D ingredient content/C ingredient	1.6	1.4	0.6	0.4
content
Sulfur content in additives	16521	14524	21544	28744
(ppm by mass)
Properties of lubricating oil
Kinematic viscosity (mm²/s)
40° C.	129.2	134.2	144.3	144.3
100° C.	14.3	14.9	15.6	15.6
Viscosity index	110	112	111	111
Elementary analysis (ppm by mass)
P	1100	1100	1100	1100
S	24000	17412	22848	30048
B	55	55	55	55
Evaluation test results
Load resistance (N)	3923	3923	4903	4903
Fatigue life (min)	1456	1581	1501	1322
Shear stability
Kinematic viscosity after shear	14.2	14.8	15.5	15.5
Decrease in viscosity (%)	0.7	0.7	0.7	0.7
Friction characteristics	0.09	0.09	0.10	0.10

	Example 21	Example 22	Example 23

Base oil composition
(% by mass on the basis of the total
amount of base oil)
A-1	(35)	—	—
A-2	—	—	(10)
A-3	(65)	—	(30)
A-4	—	(100)	—
A-6	—	—	(60)
Base oil kinematic viscosity
(mm²/s)
40° C.	54.0	46.7	115.9
100° C.	7.6	7.6	28.1
Sulfur content in base oil	4260	0	1880
(ppm by mass)
Lubricating oil composition
(% by mass on the basis of the total
amount of lubricating oil)
Base oil	Balance	Balance	Balance
B-1	3.0	3.0	3.0
C-1	1.5	1.5	1.5
D-1	2.0	2.0	2.0
E-1	0.80	0.80	0.80
G-1	5.0	5.0	5.0
D ingredient content/C ingredient	1.4	1.4	1.4
content
Sulfur content in additives	14524	14524	14524
(ppm by mass)
Properties of lubricating oil
Kinematic viscosity (mm²/s)
40° C.	78.3	79.3	144.1
100° C.	10.2	10.6	31.7
Viscosity index	112	118	262
Elementary analysis (ppm by mass)
P	1100	1100	1100
S	16580	14524	16404
B	55	55	55
Evaluation test results
Load resistance (N)	3089	3089	3923
Fatigue life (min)	1115	1217	2019
Shear stability
Kinematic viscosity after shear	10.1	10.5	31.6
Decrease in viscosity (%)	0.9	0.5	0.4
Friction characteristics	0.08	0.09	0.09

TABLE 4

	Comparative	Comparative	Comparative
	Example 1	Example 2	Example 3

Base oil composition
(% by mass on the
basis of the total
amount of base oil)
A-1	(38)	(38)	(38)
A-2	(62)	(62)	(62)
Base oil kinematic viscosity
(mm²/s)
40° C.	118.1	118.1	118.1
100° C.	12.7	12.7	12.7
Sulfur content in base oil	3508	3508	3508
(ppm by mass)
Lubricating oil composition
(% by mass on the basis of
the total amount of
lubricating oil)
Base oil	Balance	Balance	Balance
B-1	—	20.0	—
b-1	—	—	3.0
b-2	—	—	—
b-3	—	—	—
b-4	—	—	—
C-1	1.5	1.5	1.5
D-1	2.0	2.0	2.0
E-1	0.80	0.80	0.80
G-1	5.0	5.0	5.0
D ingredient content/C	1.4	1.4	1.4
ingredient content
Sulfur content in additives	14524	14524	14524
(ppm by mass)
Properties of lubricating oil
Kinematic viscosity (mm²/s)
40° C.	122.9	206.2	143.3
100° C.	13.7	21.0	15.3
Viscosity index	108	121	109
Elementary analysis
(ppm by mass)
P	1100	1100	1100
S	18032	18032	18032
B	55	55	55
Evaluation test results
Load resistance (N)	3923	3923	3923
Fatigue life (min)	659	1578	912
Shear stability
Kinematic viscosity after	13.6	19.3	15.2
shear
Decrease in viscosity (%)	0.1	8.8	0.5
Friction characteristics	0.09	0.09	0.09

	Comparative	Comparative	Comparative
	Example 4	Example 5	Example 6

Base oil composition
(% by mass on the
basis of the total
amount of base oil)
A-1	(38)	(38)	(38)
A-2	(62)	(62)	(62)
Base oil kinematic viscosity
(mm²/s)
40° C.	118.1	118.1	118.1
100° C.	12.7	12.7	12.7
Sulfur content in base oil	3508	3508	3508
(ppm by mass)
Lubricating oil composition
(% by mass on the basis of
the total amount of
lubricating oil)
Base oil	Balance	Balance	Balance
B-1	—	—	—
b-1	—	—	—
b-2	3.0	—	—
b-3	—	3.0	—
b-4	—	—	3.0
C-1	1.5	1.5	1.5
D-1	2.0	2.0	2.0
E-1	0.80	0.80	0.80
G-1	5.0	5.0	5.0
D ingredient content/C	1.4	1.4	1.4
ingredient content
Sulfur content in additives	14524	14524	14524
(ppm by mass)
Properties of lubricating oil
Kinematic viscosity (mm²/s)
40° C.	193.2	150.2	169.2
100° C.	19.8	16.0	17.2
Viscosity index	118	111	110
Elementary analysis
(ppm by mass)
P	1100	1100	1100
S	18032	18032	18032
B	55	55	55
Evaluation test results
Load resistance (N)	3923	3923	3923
Fatigue life (min)	2021	882	856
Shear stability
Kinematic viscosity after	16.6	15.5	15.5
shear
Decrease in viscosity (%)	19.6	3.6	11.4
Friction characteristics	0.09	0.09	0.09

TABLE 5

	Comparative	Comparative	Comparative	Comparative
	Example 7	Example 8	Example 9	Example 10

Base oil composition
(% by mass on the basis of the total
amount of base oil)
A-1	(38)	(38)	(38)	(10)
A-2	(62)	(62)	(62)	—
A-3	—	—	—	—
A-4	—	—	—	—
A-5	—	—	—	(90)
A-6	—	—	—	—
Base oil kinematic viscosity
(mm²/s)
40° C.	118.1	118.1	118.1	9.5
100° C.	12.7	12.7	12.7	2.6
Sulfur content in base oil	3508	3508	3508	140
(ppm by mass)
Lubricating oil composition
(% by mass on the basis of the total
amount of lubricating oil)
Base oil	Balance	Balance	Balance	Balance
B-1	3.0	3.0	3.0	3.0
C-1	—	1.5	8.0	1.5
D-1	2.0	2.0	2.0	2.0
E-1	0.80	—	0.80	0.80
G-1	5.0	5.0	5.0	5.0
G-3	—	—	—	—
D ingredient content/C ingredient	—	1.4	0.3	1.4
content
Sulfur content in additives	9182	14524	37910	14524
(ppm by mass)
Properties of lubricating oil
Kinematic viscosity (mm²/s)
40° C.	144.3	144.3	143.9	32.1
100° C.	15.6	15.6	15.5	5.4
Viscosity index	111	109	110	99
Elementary analysis (ppm by mass)
P	1100	1100	1100	1100
S	12690	18032	32252	14664
B	55	55	55	55
Evaluation test results
Load resistance (N)	1961	3923	4903	1961
Fatigue life (min)	1256	1578	728	562
Shear stability
Kinematic viscosity after shear	15.5	15.5	15.3	5.3
Decrease in viscosity (%)	0.7	0.7	0.9	0.7
Friction characteristics	0.09	0.15	0.09	0.09

	Comparative	Comparative	Comparative
	Example 11	Example 12	Example 13

Base oil composition
(% by mass on the basis of the total
amount of base oil)
A-1	(38)	(38)	(38)
A-2	(62)	(62)	(62)
A-3	—	—	—
A-4	—	—	—
A-5	—	—	—
A-6	—	—	—
Base oil kinematic viscosity
(mm²/s)
40° C.	118.1	118.1	118.1
100° C.	12.7	12.7	12.7
Sulfur content in base oil	3508	3508	3508
(ppm by mass)
Lubricating oil composition
(% by mass on the basis of the total
amount of lubricating oil)
Base oil	Balance	Balance	Balance
B-1	3.0	3.0	3.0
C-1	0.1	1.5	1.5
D-1	5.0	—	2.0
E-1	0.80	0.80	2.0
G-1	—	5.0	5.0
G-3	7.0	—	—
D ingredient content/C ingredient	71	1.4	1.4
content
Sulfur content in additives	23152	5400	14524
(ppm by mass)
Properties of lubricating oil
Kinematic viscosity (mm²/s)
40° C.	144.6	143.3	144.3
100° C.	15.8	15.4	15.6
Viscosity index	113	110	111
Elementary analysis (ppm by mass)
P	890	1100	1100
S	26660	8908	18032
B	170	55	55
Evaluation test results
Load resistance (N)	4903	1961	2452
Fatigue life (min)	908	1301	1344
Shear stability
Kinematic viscosity after shear	15.5	15.3	15.5
Decrease in viscosity (%)	2.1	0.7	0.7
Friction characteristics	0.09	0.09	0.07

Claims

1. A lubricating oil composition comprising:

a lubricating base oil;

1.0% by mass or more and 15.0% by mass or less of a dispersant poly(meth)acrylate compound having a weight average molecular weight of 20000 or more and 200000 or less;

0.05% by mass or more and 6.0% by mass or less of a thiadiazole compound;

1.5% by mass or more and 4.0% by mass or less of a polysulfide compound; and

0.2% by mass or more and 1.5% by mass or less of a friction modifier,

based on a total amount of the lubricating oil composition,

wherein a mass ratio of the polysulfide compound content to the thiadiazole compound content (polysulfide compound/thiadiazole compound) is 0.4 or more and 50 or less, and

a kinematic viscosity at 100° C. of the lubricating oil composition is 7.0 mm²/s or more and 35.0 mm²/s or less.

2. The lubricating oil composition according to claim 1, wherein the friction modifier comprises at least one selected from a group consisting of primary or secondary amide friction modifiers and primary or secondary amine friction modifiers.

3. The lubricating oil composition according to claim 1, wherein the lubricating oil composition is used for gear oils.

4. The lubricating oil composition according to claim 1, wherein the lubricating oil composition is used for final reduction gear oils.

5. The lubricating oil composition according to claim 2, wherein the lubricating oil composition is used for gear oils.

6. The lubricating oil composition according to claim 2, wherein the lubricating oil composition is used for final reduction gear oils.