LUBRICATING OIL COMPOSITION

Description

TECHNICAL FIELD

The present invention relates to a lubricating oil composition, an internal combustion engine, and a method for lubricating an internal combustion engine.

BACKGROUND ART

Internal combustion engines used in automobiles and the like are subject to various requirements, such as increased output in smaller engines, fuel efficiency and compliance with exhaust gas regulations, and lubricating oil compositions used for internal combustion engines are being developed to meet such requirements.

For example, Patent Literature 1 discloses an invention relating to a lubricating oil composition containing 14 mass % or more of a fraction having a boiling point of 500 to 550° C. and 5 mass % or more of a fraction having a boiling point exceeding 550° C., for the purpose of providing a lubricating oil composition having a further improved performance in suppressing compressor deposit formation.

CITATION LIST

Patent Literature

• • Patent Literature 1: JP 2016-196595 A

SUMMARY OF INVENTION

Technical Problem

Meanwhile, as a measure for environmental compliance, superchargers equipped with an EGR system that re-intakes and recirculates a portion of the exhaust gas, are under development. In superchargers equipped with an EGR system, increasing the boost pressure tends to generate deposits derived from engine oil, which reduces the efficiency of the supercharger. Furthermore, the internal combustion engines used in automobiles and the like are required to be fuel-efficient.

Under these circumstances, there is a need for a lubricating oil composition that can be suitably used for an internal combustion engine, is highly effective in suppressing deposit formation, and has excellent fuel efficiency, regardless of the use environment.

Solution to Problem

As a result of extensive studies, the present inventors have found that a lubricating oil composition using a base oil in which the content proportion of heavy fraction (Hf) having 32 or more carbon atoms is adjusted to a predetermined range, and a metal-based detergent containing an overbased calcium salicylate of a predetermined base number in a predetermined ratio can solve the above problem. Specifically, the present invention discloses the following embodiments.

[1] A lubricating oil composition comprising: a base oil (A); and a metal-based detergent (B),

• • wherein a content proportion of heavy fraction (Hf) having 32 or more carbon atoms in the component (A) is 14.0 mass % or more based on the total amount of the component (A),
  • the component (B) comprises an overbased calcium salicylate (B1) with a base number of 100 mg KOH/g or more, and
  • a content proportion of the component (B1) in the component (B) is 35.0 mass % or more based on the total amount of the component (B).
    [2] An internal combustion engine, which is filled with the lubricating oil composition according to the above [1].
    [3] A method for lubricating an internal combustion engine, wherein the lubricating oil composition according to the above [1] is applied to the lubrication of an internal combustion engine.

Advantageous Effects of Invention

The lubricating oil composition of a preferred embodiment of the present invention has excellent efficacy in suppressing deposit formation, detergency, stability, as well as fuel efficiency, regardless of the use environment. Therefore, the lubricating oil composition of one embodiment of the present invention can be suitably used for lubrication of an internal combustion engine, for example.

DESCRIPTION OF EMBODIMENTS

Regarding the numerical range described in the present specification, the upper limit and the lower limit can be arbitrarily combined. For example, with the description “preferably 30 to 100, more preferably 40 to 80” as a numerical range, the range of “30 to 80” and the range of “40 to 100” are also included in the numerical range described in the present specification.

In addition, for example, with the description “preferably 30 or more, more preferably 40 or more, and preferably 100 or less, more preferably 80 or less” as a numerical range, the range of “30 to 80” and the range of “40 to 100” are also included in the numerical range described in the present specification. That is, in defining the upper limit values and lower limit values described in the present specification, the numerical range from the lower limit value to the upper limit value can be defined by appropriately selecting from each option and combining them arbitrarily.

Furthermore, for example, the description of “60 to 100” as the numerical range described in the present specification means a range of “60 or more (60 or more than 60) and 100 or less (100 or less than 100)”.

In addition, the various requirements described in the present specification as preferred embodiments can be combined in multiple combinations.

[Constitution of Lubricating Oil Composition]

The lubricating oil composition of one embodiment of the present invention contains a specific base oil (A) and a specific metal-based detergent (B), but may further contain components as long as the effects of the present invention are not impaired.

For example, from the viewpoint of obtaining a lubricating oil composition with a low temperature dependence of viscosity and good fuel efficiency, the lubricating oil composition of one embodiment of the present invention may further contain a viscosity index improver (C).

In the lubricating oil composition of one embodiment of the present invention, the total content of the components (A) and (B) is preferably 50 mass % or more, more preferably 60 mass % or more, more preferably 65 mass % or more, still more preferably 70 mass % or more, still more preferably 75 mass % or more, still much more preferably 80 mass % or more, and particularly preferably 83 mass % or more, and may be 100 mass % or less, 99.9 mass % or less, 99.0 mass % or less, 97.0 mass % or less, 95.0 mass % or less, 92.0 mass % or less, or 90.0 mass % or less, based on the total amount (100 mass %) of the lubricating oil composition.

In the lubricating oil composition of one embodiment of the present invention, the total content of the components (A), (B) and (C) is preferably 55 mass % or more, more preferably 60 mass % or more, more preferably 65 mass % or more, still more preferably 70 mass % or more, still more preferably 75 mass % or more, still much more preferably 80 mass % or more, and particularly preferably 85 mass % or more, and may be 100 mass % or less, 99.9 mass % or less, 99.0 mass % or less, 97.0 mass % or less, 95.0 mass % or less, 92.0 mass % or less, or 90.0 mass % or less, based on the total amount (100 mass %) of the lubricating oil composition.

Details of the components contained in the lubricating oil composition of one embodiment of the present invention will be described hereinafter.

<Component (A): Base Oil>

In the lubricating oil composition of one embodiment of the present invention, examples of the base oil used as the component (A) include one or more selected from mineral oils and synthetic oils.

Examples of the mineral oils include atmospheric residues obtained by subjecting crude oils, such as paraffinic crude oil, intermediate base crude oil and naphthenic crude oil, to atmospheric distillation; distillates obtained by subjecting these atmospheric residues to vacuum distillation; and refined oils obtained by subjecting the distillates to one or more of refining treatments, such as solvent deasphalting, solvent extraction, hydrocracking, solvent dewaxing, catalytic dewaxing, and hydrorefining.

Examples of the synthetic oils include poly-α-olefins, such as an α-olefin homopolymer and an α-olefin copolymer (for example, an α-olefin copolymer having 8 to 14 carbon atoms such as an ethylene-α-olefin copolymer); isoparaffin; polyalkylene glycol; ester oils, such as polyol ester, dibasic acid ester, and phosphoric acid ester; ether oils, such as polyphenyl ether; alkylbenzene; alkylnaphthalene; and synthetic oil (GTL) obtained by isomerizing wax (GTL WAX (Gas To Liquids WAX)) produced from natural gas through Fischer-Tropsch process or the like.

The base oil (A) used in one embodiment of the present invention satisfies the following requirement (I).

Requirement (I): the content proportion of heavy fraction (Hf) having 32 or more carbon atoms in the component (A) is 14.0 mass % or more based on the total amount of the component (A).

By using the base oil (A) adjusted to meet the requirement (I), a lubricating oil composition with good fluidity and suppressed evaporation can be obtained even when used in high temperature and/or high pressure environments where base oils tend to evaporate. As a result, the lubricating oil composition of one embodiment of the present invention having good fluidity allows to spread the metal-based detergent, component (B), over the lubricated surface and to effectively suppress deposit formation.

On the other hand, lubricating oil compositions in which the content proportion of heavy fraction (Hf) having 32 or more carbon atoms in the component (A) is less than 14.0 mass % tend to poorly suppress evaporation under high temperature and/or high pressure environments, resulting in reduced fluidity and inadequate suppression of deposit formation.

From the viewpoint of obtaining a lubricating oil composition that retains good fluidity and is highly effective in suppressing deposit formation even when used under high temperature and/or high pressure environments, the content proportion of heavy fraction (Hf) having 32 or more carbon atoms is preferably 15.0 mass % or more, more preferably 16.0 mass % or more, still more preferably 17.0 mass % or more, still much more preferably 18.0 mass % or more, and particularly preferably 19.0 mass % or more, and from the viewpoint of obtaining a lubricating oil composition with good fuel efficiency, it is preferably 40.0 mass % or less, more preferably 37.0 mass % or less, more preferably 35.0 mass % or less, more preferably 33.0 mass % or less, still more preferably 30.0 mass % or less, still more preferably 27.0 mass % or less, still much more preferably 25.0 mass % or less, and particularly preferably 23.0 mass % or less, based on the total amount (100 mass %) of the component (A).

In addition, the base oil (A) used in one embodiment of the present invention preferably satisfies at least one of the following requirements (II) and (III), and more preferably satisfies both of the following requirements (II) and (III).

Requirement (II): the content ratio by mass of the light fraction (Lf) having 21 or less carbon atoms to the heavy fraction (Hf) having 32 or more carbon atoms in the component (A), [(Lf)/(Hf)], is 0.05 or more.
Requirement (III): the content proportion of light fraction (Lf) having 21 or less carbon atoms in the component (A) is 1.0 mass % or more based on the total amount of the component (A).

By using a base oil (A) adjusted to meet the requirements (II) and/or (III), a lubricating oil composition with improved fuel efficiency can be obtained.

From the viewpoint of obtaining a lubricating oil composition with further improved fuel efficiency, the content ratio by mass [(Lf)/(Hf)] is preferably 0.07 or more, more preferably 0.09 or more, more preferably 0.10 or more, still more preferably 0.11 or more, still much more preferably 0.12 or more, and particularly preferably 0.13 or more, and furthermore, may be 0.15 or more, 0.17 or more, 0.20 or more, 0.23 or more, 0.25 or more, 0.27 or more, or 0.30 or more.

In addition, from the viewpoint of obtaining a lubricating oil composition that better retains good fluidity and is more effective in suppressing deposit formation even when used under high temperature and/or high pressure environments, the content ratio by mass [(Lf)/(Hf)] is preferably 0.80 or less, more preferably 0.70 or less, more preferably 0.60 or less, still more preferably 0.55 or less, still much more preferably 0.50 or less, and particularly preferably 0.48 or less.

From the viewpoint of obtaining a lubricating oil composition with further improved fuel efficiency, the content proportion of light fraction (Lf) having 21 or less carbon atoms is preferably 1.5 mass % or more, more preferably 1.7 mass % or more, still more preferably 2.0 mass % or more, still much more preferably 2.3 mass % or more, and particularly preferably 2.5 mass % or more, and furthermore, may be 2.7 mass % or more, 3.0 mass % or more, 3.5 mass % or more, 4.0 mass % or more, 4.5 mass % or more, 5.0 mass % or more, 5.5 mass % or more, 6.0 mass % or more, 6.5 mass % or more, or 7.0 mass % or more, based on the total amount (100 mass %) of the component (A).

In addition, from the viewpoint of obtaining a lubricating oil composition that better retains good fluidity and is more effective in suppressing deposit formation even when used under high temperature and/or high pressure environments, the content proportion of light fraction (Lf) having 21 or less carbon atoms is preferably 25.0 mass % or less, more preferably 20.0 mass % or less, more preferably 17.0 mass % or less, more preferably 15.0 mass % or less, still more preferably 12.0 mass % or less, still more preferably 10.0 mass % or less, still much more preferably 9.5 mass % or less, and particularly preferably 9.0 mass % or less, based on the total amount (100 mass %) of the component (A).

The content proportion of middle fraction (Mf) having 22 or more and 31 or less carbon atoms in the component (A) used in one embodiment of the present invention is preferably 35.0 mass % or more, more preferably 40.0 mass % or more, more preferably 45.0 mass % or more, still more preferably 50.0 mass % or more, still more preferably 55.0 mass % or more, still much more preferably 60.0 mass % or more, and particularly preferably 65.0 mass % or more, and it is preferably 85 mass % or less, more preferably 83.5 mass % or less, more preferably 81.0 mass % or less, still more preferably 80.0 mass % or less, still more preferably 79.0 mass % or less, still much more preferably 78.0 mass % or less, and particularly preferably 77.0 mass % or less, based on the total amount (100 mass %) of the component (A).

In the present specification, the contents of the components with each number of carbon atoms constituting the component (A), the content proportion of heavy fraction (Hf) having 32 or more carbon atoms, the content proportion of light fraction (Lf) having 21 or less carbon atoms, and the content proportion of middle fraction (Mf) having 22 or more and 31 or less carbon atoms mean the values measured in accordance with the method described in the Examples.

The kinematic viscosity of the component (A) used in one embodiment of the present invention at 40° C. is preferably 10 to 120 mm²/s, more preferably 15 to 100 mm²/s, more preferably 20 to 80 mm²/s, still more preferably 25 to 70 mm²/s, still much more preferably 30 to 60 mm²/s, and particularly preferably 35 to 50 mm²/s.

The viscosity index of the component (A) used in one embodiment of the present invention is preferably 80 or more, more preferably 100 or more, still more preferably 110 or more, still much more preferably 120 or more, and particularly preferably 130 or more.

The kinematic viscosity and the viscosity index mean values measured and calculated in accordance with JIS K2283:2000.

When a mixed oil that is a combination of two or more base oils is used as the component (A) in one embodiment of the present invention, the kinematic viscosity and the viscosity index of the mixed oil are preferably in the above ranges. In addition, the weighted averages of the kinematic viscosity and the viscosity index calculated from the content proportion of the base oil constituting the mixed oil are preferably in the above ranges.

In the lubricating oil composition of one embodiment of the present invention, the content of the component (A) is preferably 40 mass % or more, more preferably 50 mass % or more, more preferably 60 mass % or more, still more preferably 65 mass& or more, still more preferably 70 mass % or more, still much more preferably 75 mass % or more, and particularly preferably 80 mass % or more, and may be 99.9 mass % or less, 99.5 mass % or less, 99.0 mass % or less, 97.0 mass % or less, 95.0 mass % or less, 92.0 mass % or less, or 90.0 mass % or less, based on the total amount (100 mass %) of the lubricating oil composition.

<Component (B): Metal-Based Detergent>

The lubricating oil composition of one embodiment of the present invention contains a metal-based detergent (B) containing an overbased calcium salicylate (B1) with a base number of 100 mg KOH/g or more.

The component (B) and the component (B1) used in one embodiment of the present invention may be used singly, or may be used in combination of two or more.

By containing an overbased calcium salicylate (B1) as the metal-based detergent (B), a lubricating oil composition with improved detergency and stability under high temperature environments, as well as excellent fuel efficiency, can be obtained.

The component (B) used in one embodiment of the present invention may be used singly, or may be used in combination of two or more.

In the lubricating oil composition of one embodiment of the present invention, the content proportion of the component (B1) in the component (B) is 35.0 mass % or more, based on the total amount (100 mass %) of the component (B) contained in the lubricating oil composition, from the viewpoint of obtaining a lubricating oil composition with improved detergency and stability under high temperature environments, as well as excellent fuel efficiency.

A lubricating oil composition in which the content proportion of the component (B1) is less than 35.0 mass % is prone to problems with detergency and stability under high temperature environments, and may also have reduced fuel efficiency.

From the above viewpoint, the content proportion of the component (B1) in the component (B) is preferably 37.0 mass or more, more preferably 40.0 mass % or more, and from the viewpoint of obtaining a lubricating oil composition with better fuel efficiency, it is more preferably 45.0 mass % or more, still more preferably 50.0 mass % or more, still more preferably 55.0 mass % or more, still much more preferably 60.0 mass % or more, and particularly preferably 63.0 mass % or more, and may be 100 mass % or less, 99.0 mass % or less, 98.0 mass % or less, 95.0 mass % or less, 90.0 mass % or less, 85.0 mass % or less, 80.0 mass % or less, 75.0 mass % or less, or 70.0 mass % or less, based on the total amount (100 mass %) of the component (B) contained in the lubricating oil composition.

As the component (B1) used in one embodiment of the present invention, for example, a compound represented by the following general formula (b-1) can be mentioned.

In the above general formula (b-1), R is a hydrogen atom or a hydrocarbon group having 1 to 18 carbon atoms.

Examples of the hydrocarbon groups that can be selected as R include an alkyl group having 1 to 18 carbon atoms, an alkenyl group having 1 to 18 carbon atoms, a cycloalkyl group having 3 to 18 ring-forming carbon atoms, an aryl group having 6 to 18 ring-forming carbon atoms, an alkylaryl group having 7 to 18 carbon atoms, and an arylalkyl group having 7 to 18 carbon atoms.

The component (B1) used in one embodiment of the present invention is overbased and therefore has a base number of 100 mg KOH/g or more.

From the viewpoint of obtaining a lubricating oil composition with further improved detergency and stability under high temperature environments, as well as better fuel efficiency, the base number of the component (B1) used in one embodiment of the present invention is preferably 120 mg KOH/g or more, more preferably 150 mg KOH/g or more, more preferably 170 mg KOH/g or more, still more preferably 200 mg KOH/g or more, still more preferably 220 mg KOH/g or more, still much more preferably 250 mg KOH/g or more, and particularly preferably 270 mg KOH/g or more, and may be 600 mg KOH/g or less, 550 mg KOH/g or less, 500 mg KOH/g or less, 450 mg KOH/g or less, or 400 mg KOH/g or less.

In the present specification, the “base number” means the value measured by perchloric acid method in accordance with “9. Potentiometric titration method (base number/perchloric acid method)” of JIS K2501 “Petroleum products and lubricants-Determination of neutralization number.”

From the viewpoint of obtaining a lubricating oil composition with further improved detergency and stability under high temperature environments, and better fuel efficiency, the content of the component (B1) in terms of calcium atoms in the lubricating oil composition of one embodiment of the present invention is preferably 0.01 mass % or more, more preferably 0.05 mass % or more, more preferably 0.07 mass % or more, still more preferably 0.10 mass % or more, still much more preferably 0.12 mass % or more, and particularly preferably 0.14 mass % or more, and is preferably 0.80 mass % or less, 0.70 mass % or less, 0.60 mass % or less, 0.50 mass % or less, 0.40 mass % or less, 0.30 mass % or less, 0.25 mass % or less, 0.22 mass % or less, or 0.20 mass % or less, based on the total amount (100 mass %) of the lubricating oil composition.

In the present specification, the content of calcium atoms (Ca) means a value measured in accordance with JPI-5S-38-92.

In the lubricating oil composition of one embodiment of the present invention, from the viewpoint of obtaining a lubricating oil composition with further improved detergency and stability under high temperature environments, and better fuel efficiency, the content of the component (B1) is preferably 0.10 mass % or more, more preferably 0.50 mass % or more, more preferably 0.70 mass % or more, still more preferably 1.00 mass % or more, still much more preferably 1.20 mass % or more, and particularly preferably 1.40 mass % or more, and is preferably 8.00 mass % or less, 7.00 mass % or less, 6.00 mass % or less, 5.00 mass % or less, 4.00 mass % or less, 3.00 mass % or less, 2.50 mass % or less, 2.20 mass % or less, or 2.00 mass % or less, based on the total amount (100 mass %) of the lubricating oil composition.

The lubricating oil composition of one embodiment of the present invention may or may not contain a metal-based detergent (B2) other than the component (B1) as the component (B).

If a component (B2) is contained, the component (B2) may be used singly, or may be used in combination of two or more.

Examples of the component (B2) used in one embodiment of the present invention include metal salt compounds of organic acids containing a metal atom selected from alkali metals and alkaline earth metals, with specific examples including metal salicylates (excluding overbased calcium salicylate which corresponds to the component (B1)), metal phenates, and metal sulfonates containing a metal atom selected from alkali metals and alkaline earth metals.

The metal atom contained in the metal-based detergent is preferably sodium, calcium, magnesium, or barium, and more preferably calcium, from the viewpoint of obtaining a lubricating oil composition having further improved high temperature detergency.

The component (B2) used in one embodiment of the present invention may be either a neutral salt having a base number of less than 100 mg KOH/g, an overbased salt having a base number of 100 mg KOH/g or more, or a mixture thereof.

The base number of the component (B2) used in one embodiment of the present invention is preferably 0 to 600 mg KOH/g, more preferably 10 to 600 mg KOH/g, and still more preferably 20 to 500 mg KOH/g.

From the viewpoint of obtaining a lubricating oil composition with further improved detergency and stability under high temperature environments, and better fuel efficiency, the component (B) used in the lubricating oil composition of one embodiment of the present invention preferably contains the component (B1) and a neutral metal sulfonate with a base number of less than 100 mg KOH/g, and more preferably contains the component (B1) and a neutral calcium sulfonate with a base number of less than 100 mg KOH/g.

In the lubricating oil composition of one embodiment of the present invention, the content of the component (B) in terms of metal atoms is preferably 0.01 mass % or more, more preferably 0.05 mass % or more, more preferably 0.07 mass % or more, still more preferably 0.10 mass % or more, still much more preferably 0.12 mass % or more, and particularly preferably 0.14 mass % or more, and is preferably 1.00 mass % or less, 0.90 mass % or less, 0.80 mass % or less, 0.70 mass % or less, 0.60 mass % or less, 0.50 mass % or less, 0.40 mass % or less, 0.30 mass % or less, 0.25 mass % or less, or 0.20 mass % or less, based on the total amount (100 mass %) of the lubricating oil composition.

In the present specification, the content of metal atoms means a value measured in accordance with JPI-5S-38-92.

In the lubricating oil composition of one embodiment of the present invention, the content of the component (B) is preferably 0.10 mass % or more, more preferably 0.50 mass % or more, more preferably 1.00 mass % or more, still more preferably 1.50 mass % or more, still much more preferably 1.70 mass % or more, and particularly preferably 2.00 mass % or more, and may be 8.00 mass % or less, 7.00 mass % or less, 6.00 mass % or less, 5.00 mass % or less, 4.00 mass % or less, 3.70 mass % or less, 3.50 mass % or less, 3.20 mass % or less, 3.00 mass % or less, 2.70 mass % or less, or 2.50 mass % or less, based on the total amount (100 mass %) of the lubricating oil composition.

<Component (C): Viscosity Index Improver>

The lubricating oil composition of one embodiment of the present invention may contain a viscosity index improver as the component (C). By containing the viscosity index improver (C), a lubricating oil composition with a low temperature dependence of viscosity and good fuel efficiency can be obtained.

The component (C) used in one embodiment of the present invention may be used singly, or may be used in combination of two or more.

Examples of the component (C) used in one embodiment of the present invention include polymers such as non-dispersed polymethacrylate, dispersed polymethacrylate, an olefin copolymer (e.g., ethylene-propylene copolymer), a dispersed olefin copolymer, and a styrene copolymer (e.g., styrene-diene copolymer and styrene-isoprene copolymer).

The component (C) used in one embodiment of the present invention may be a comb-shaped polymer having a structure in which the main chain has many trifurcation points from which high molecular weight side chains are arising, or it may be a star-shaped polymer having a structure in which one atom such as a carbon atom is bonded to three or more chain polymers.

From the viewpoint of obtaining a lubricating oil composition with a low temperature dependence of viscosity and good fuel efficiency, as well as adjusting the viscosity grade of the lubricating oil composition to a viscosity grade of 0 W-20 according to SAE J300:2015, it is preferable to use a combination of a comb-shaped polymer and dispersed polymethacrylate as the component (C) used in one embodiment of the present invention.

The content ratio of the comb-shaped polymer to the dispersed polymethacrylate, [comb-shaped polymer/dispersed polymethacrylate], is preferably 20/80 or more, more preferably 40/60 or more, more preferably 55/45 or more, still more preferably 65/35 or more, still more preferably 75/25 or more, still much more preferably 80/20 or more, and particularly preferably 85/15 or more, and is preferably 99/1 or less, more preferably 98/2 or less, still more preferably 97/3 or less, still much more preferably 96/4 or less, and particularly preferably 95/5 or less.

From the viewpoint of obtaining a lubricating oil composition with a low temperature dependence of viscosity and good fuel efficiency, as well as adjusting the viscosity grade of the lubricating oil composition to a viscosity grade of 0 W-30 according to SAE J300:2015, it is preferable to use a combination of non-dispersed polymethacrylate and dispersed polymethacrylate as the component (C) used in one embodiment of the present invention.

The content ratio of the non-dispersed polymethacrylate to the dispersed polymethacrylate, [non-dispersed polymethacrylate/dispersed polymethacrylate], is preferably 20/80 or more, more preferably 40/60 or more, more preferably 55/45 or more, still more preferably 65/35 or more, still more preferably 75/25 or more, still much more preferably 80/20 or more, and particularly preferably 85/15 or more, and preferably 99/1 or less, more preferably 98/2 or less, still more preferably 97/3 or less, still much more preferably 96/4 or less, and particularly preferably 95/5 or less.

The weight-average molecular weight (Mw) of the viscosity index improver used in one embodiment of the present invention is, from the viewpoint of obtaining a lubricating oil composition with a low temperature dependence of viscosity and good fuel efficiency, preferably 10,000 or more, more preferably 30,000 or more, more preferably 50,000 or more, still more preferably 70,000 or more, still more preferably 100,000 or more, still much more preferably 120,000 or more, and particularly preferably 150,000 or more, and furthermore, may be 170,000 or more, 200,000 or more, 250,000 or more, or 300,000 or more, and from the viewpoint of obtaining a lubricating oil composition that can suppress deposit formation, it may be 1,000,000 or less, 900,000 or less, 800,000 or less, 700,000 or less, 650,000 or less, 600,000 or less, 550,000 or less, or 500,000 or less.

In the lubricating oil composition of one embodiment of the present invention, the content of the component (C) in terms of resin is preferably 0.01 mass % or more, more preferably 0.10 mass % or more, more preferably 0.30 mass % or more, more preferably 0.50 mass % or more, still more preferably 0.70 mass % or more, still more preferably 0.90 mass % or more, still much more preferably 1.10 mass % or more, and particularly preferably 1.30 mass % or more, based on the total amount (100 mass %) of the lubricating oil composition, from the viewpoint of obtaining a lubricating oil composition with a low temperature dependence of viscosity and good fuel efficiency.

From the viewpoint of obtaining a lubricating oil composition that can suppress deposit formation, the content of the component (C) in terms of resin is preferably 4.0 mass % or less, more preferably 3.5 mass % or less, more preferably 3.0 mass % or less, still more preferably 2.5 mass % or less, still much more preferably 2.2 mass % or less, and particularly preferably 2.0 mass % or less, based on the total amount (100 mass %) of the lubricating oil composition.

The component (C) used in one embodiment of the present invention and the pour point depressant and anti-foaming agent described later are usually commercially available in the form of solutions dissolved by diluent oils such as mineral oils or synthetic oils, taking into consideration handling and solubility with the component (A). In the present specification, the contents of the component (C), the pour point depressant and the anti-foaming agent means the content in terms of solid excluding the diluent oil.

<Lubricating Oil Additive>

The lubricating oil composition of one embodiment of the present invention may further contain a lubricating oil additive other than the components (B) to (C) when needed as long as the effects of the present invention are not impaired.

Examples of such lubricating oil additives include a pour point depressant, an antioxidant, a friction modifier, an anti-wear agent, an extreme pressure agent, a metal deactivator, an ashless dispersant, an anti-rust agent, and an anti-foaming agent.

These lubricating oil additives may be each used singly, or may be each used in combination of two or more.

The contents of these lubricating oil additives can be each appropriately adjusted as long as the effects of the present invention are not impaired, and the contents of the additives are each independently usually 0.001 to 15 mass %, preferably 0.005 to 10 mass %, and more preferably 0.01 to 5 mass %, based on the total amount (100 mass %) of the lubricating oil composition.

[Pour Point Depressant]

The lubricating oil composition of one embodiment of the present invention may further contain a pour point depressant. The pour point depressant may be used singly, or may be used in combination of two or more.

Examples of the pour point depressants used in one embodiment of the present invention include an ethylene-vinyl acetate copolymer, a condensate of chlorinated paraffin and naphthalene, a condensate of chlorinated paraffin and phenol, polymethacrylate, and polyalkylstyrene.

The mass-average molecular weight (Mw) of the pour point depressant used in one embodiment of the present invention may be 5,000 or more, 7,000 or more, 10,000 or more, 15,000 or more, 20,000 or more, 25,000 or more, 30,000 or more, 35,000 or more, 40,000 or more, 45,000 or more, 50,000 or more, 55,000 or more, or 60,000 or more, and may be 150,000 or less, 120,000 or less, 100,000 or less, 90,000 or less, or 80,000 or less.

[Antioxidant]

The lubricating oil composition of one embodiment of the present invention may further contain an antioxidant. The antioxidant may be used singly, or may be used in combination of two or more.

Examples of the antioxidants used in one embodiment of the present invention include amine antioxidants, such as alkylated diphenylamine, phenylnaphthylamine, and alkylated phenylnaphthylamine; phenolic antioxidants, such as 2,6-di-t-butylphenol, 4,4′-methylenebis(2,6-di-t-butylphenol), isooctyl-3-(3,5-di-t-butyl-4-hydroxyphenyl) propionate, and n-octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl) propionate; and sulfur antioxidants, such as phenothiazine, dioctadecyl sulfide, dilauryl-3,3′-thiodipropionate, and 2-mercaptobenzimidazole.

[Friction Modifier and Anti-Wear Agent]

The lubricating oil composition of one embodiment of the present invention may further contain a friction modifier or an anti-wear agent. The friction modifier or anti-wear agent may be used singly, or may be used in combination of two or more.

Examples of the friction modifiers and anti-wear agents used in one embodiment of the present invention include sulfur compounds such as a sulfurized olefin, a dialkyl polysulfide, a diarylalkyl polysulfide, and a diaryl polysulfide; phosphorous compounds such as a phosphoric acid ester, a thiophosphoric acid ester, a phosphorous acid ester, an alkylhydrogen phosphite, an amine salt of phosphoric acid ester, and an amine salt of phosphorous acid ester; organic molybdenum compounds such as molybdenum dithiocarbamate (MoDTC), molybdenum dithiophosphate (MoDTP), and an amine salt of molybdic acid; organic zinc compounds such as zinc dithiophosphate (ZnDTP) and zinc dithiocarbamate (ZnDTC); and ashless friction modifiers such as an amine compound, a fatty acid ester, a fatty acid amide, a fatty acid, an aliphatic alcohol, an aliphatic ether, an urea compound, and a hydrazide compound.

[Extreme Pressure Agent]

The lubricating oil composition of one embodiment of the present invention may further contain an extreme pressure agent. The extreme pressure agent may be used singly, or may be used in combination of two or more. Examples of the extreme pressure agents used in one embodiment of the present invention include sulfur compounds such as a sulfurized olefin, a dialkyl polysulfide, a diarylalkyl polysulfide, and a diaryl polysulfide; and phosphorous compounds such as a phosphoric acid ester, a thiophosphoric acid ester, a phosphorous acid ester, an alkylhydrogen phosphite, an amine salt of phosphoric acid ester, and an amine salt of phosphorous acid ester.

[Metal Deactivator]

The lubricating oil composition of one embodiment of the present invention may further contain a metal deactivator. The metal deactivator may be used singly, or may be used in combination of two or more.

Examples of the metal deactivators used in one embodiment of the present invention include benzotriazole, a triazole derivative, a benzotriazole derivative, and a thiadiazole derivative.

[Ashless Dispersant]

The lubricating oil composition of one embodiment of the present invention may further contain an ashless dispersant from the viewpoint of having good dispersing ability. The ashless dispersant may be used singly, or may be used in combination of two or more.

The ashless dispersant used in one embodiment of the present invention is preferably an alkenyl succinimide, and examples thereof include an alkenyl bis-succinimide represented by the following general formula (f-1) and an alkenyl monosuccinimide represented by the following general formula (f-2).

In the above general formulae (f-1) and (f-2), R^f1, R^f2 and R^f3 are each independently an alkenyl group having a mass-average molecular weight (Mw) of 500 to 3000 (preferably 900 to 2500).

Examples of the alkenyl groups that can be selected as R^f1, R^f2 and R^f3 include a polybutenyl group, a polyisobutenyl group, and an ethylene-propylene copolymer, and among these, a polybutenyl group or a polyisobutenyl group is preferable.

A^f1, A^f2 and A^f3 are each independently an alkylene group having 2 to 5 carbon atoms.

x1 is an integer of 0 to 10, preferably an integer of 1 to 4, and more preferably 2 or 3.

x2 is an integer of 1 to 10, preferably an integer of 2 to 5, and more preferably 3 or 4.

The compound represented by the aforementioned general formula (f-1) or (f-2) may be a modified alkenyl succinimide reacted with one or more selected from a boron compound, an alcohol, an aldehyde, a ketone, an alkylphenol, a cyclic carbonate, an epoxy compound, an organic acid, and the like.

[Anti-Rust Agent]

The lubricating oil composition of one embodiment of the present invention may further contain an anti-rust agent. The anti-rust agent may be used singly, or may be used in combination of two or more.

Examples of the anti-rust agents used in one embodiment of the present invention include a fatty acid, an alkenyl succinic acid half ester, a fatty acid soap, an alkyl sulfonic acid salt, a polyhydric alcohol fatty acid ester, a fatty acid amine, oxidized paraffin, and an alkyl polyoxyethylene ether.

[Anti-Foaming Agent]

The lubricating oil composition of one embodiment of the present invention may further contain an anti-foaming agent. The anti-foaming agent may be used singly, or may be used in combination of two or more.

Examples of the anti-foaming agents used in one embodiment of the present invention include an alkyl silicone anti-foaming agent, a fluorosilicone anti-foaming agent, and a fluoroalkyl ether anti-foaming agent.

<Method for Producing Lubricating Oil Composition>

The method for producing a lubricating oil composition of one embodiment of the present invention is not particularly limited, but from the viewpoint of productivity, the method is preferably a method having a step of adding, if needed, the components (B) and (C), as well as the other lubricating oil additives, to the base oil (A).

[Properties of Lubricating Oil Composition]

From the viewpoint of obtaining a lubricating oil composition with better fuel efficiency, the kinematic viscosity of the lubricating oil composition of one embodiment of the present invention at 40° C. is preferably 50.0 mm²/s or less, more preferably 47.0 mm²/s or less, still more preferably 45.0 mm²/s or less, and preferably 5.0 mm²/s or more, more preferably 10.0 mm²/s or more, still more preferably 15.0 mm²/s or more, still much more preferably 20.0 mm²/s or more, and particularly preferably 25.0 mm²/s or more.

From the viewpoint of obtaining a lubricating oil composition with better fuel efficiency, the kinematic viscosity of the lubricating oil composition of one embodiment of the present invention at 100° C. is preferably 15.0 mm²/s or less, more preferably 13.0 mm²/s or less, still more preferably 11.0 mm²/s or less, and preferably 3.0 mm²/s or more, more preferably 4.0 mm²/s or more, and still more preferably 5.0 mm²/s or more.

The viscosity index of the lubricating oil composition of one embodiment of the present invention is preferably 130 or more, more preferably 140 or more, more preferably 150 or more, still more preferably 160 or more, still much more preferably 170 or more, and particularly preferably 180 or more.

The viscosity grade of the lubricating oil composition of one embodiment of the present invention may be 0 W-20 to 0 W-30, as classified according to SAE J300:2015.

When the lubricating oil composition of one embodiment of the present invention has a viscosity grade of 0 W-20 according to SAE J300:2015, the kinematic viscosity of the lubricating oil composition at 40° C. is preferably 40.0 mm²/s or less, more preferably 37.0 mm²/s or less, still more preferably 35.0 mm²/s or less, and preferably 22.0 mm²/s or more, more preferably 25.0 mm²/s or more, and still more preferably 27.0 mm²/s or more from the viewpoint of obtaining a lubricating oil composition with better fuel efficiency.

When the lubricating oil composition of one embodiment of the present invention has a viscosity grade of 0 W-20 according to SAE J300:2015, the kinematic viscosity of the lubricating oil composition at 100° C. is preferably 8.0 mm²/s or less, more preferably 7.7 mm²/s or less, still more preferably 7.5 mm²/s or less, and preferably 5.5 mm²/s or more, more preferably 6.0 mm²/s or more, and still more preferably 6.5 mm²/s or more from the viewpoint of obtaining a lubricating oil composition with better fuel efficiency.

When the lubricating oil composition of one embodiment of the present invention has a viscosity grade of 0 W-30 according to SAE J300:2015, the kinematic viscosity of the lubricating oil composition at 40° C. is preferably 45.0 mm²/s or less, more preferably 44.0 mm²/s or less, and preferably 25.0 mm²/s or more, more preferably 30.0 mm²/s or more, still more preferably 35.0 mm²/s or more, and still much more preferably 40.0 mm²/s or more from the viewpoint of obtaining a lubricating oil composition with better fuel efficiency.

When the lubricating oil composition of one embodiment of the present invention has a viscosity grade of 0 W-30 according to SAE J300:2015, the kinematic viscosity of the lubricating oil composition at 100° C. is preferably 10.0 mm²/s or less, more preferably 9.8 mm²/s or less, and preferably 6.0 mm²/s or more, more preferably 7.0 mm²/s or more, still more preferably 8.0 mm²/s or more, and still much more preferably 9.0 mm²/s or more from the viewpoint of obtaining a lubricating oil composition with better fuel efficiency.

The HTHS viscosity of the lubricating oil composition of one embodiment of the present invention at 150° C. is, from the viewpoint of obtaining a lubricating oil composition with improved oil film-retaining properties under high temperature environments, and excellent wear resistance, preferably 2.5 mPa·s or more, more preferably 2.6 mPa·s or more, and from the viewpoint of obtaining a lubricating oil composition with good fuel efficiency under high temperature environments, and suitable for use under high pressure environments, preferably 3.7 mPa·s or less, more preferably 3.5 mPa·s or less, still more preferably 3.4 mPa·s or less, still much more preferably 3.3 mPa·s or less, and particularly preferably 3.2 mPa·s or less.

In the present specification, the HTHS viscosity at 150° C. means a value measured at 150° C. in accordance with ASTM D4683.

The residual oil content of the lubricating oil composition of one embodiment of the present invention, as measured and calculated based on the method described in the Examples described later, is preferably 25.0 mass % or more, more preferably 26.0 mass % or more, still more preferably 27.0 mass % or more, and still much more preferably 28.0 mass& or more, from the viewpoint of obtaining a lubricating oil composition that retains good fluidity and is highly effective in suppressing deposit formation even when used under high temperature and/or high pressure environments.

The SRV coefficient of friction of the lubricating oil composition of one embodiment of the present invention, as measured based on the method described in the Examples described later, is preferably 0.08 or less, more preferably 0.07 or less, still more preferably 0.06 or less, and still much more preferably 0.05 or less.

The rating for the lubricating oil composition of one embodiment of the present invention, in a hot tube test performed in accordance with JPI-5S-55-99, is preferably 7.0 or more, more preferably 7.5 or more, still more preferably 8.0 or more, and still much more preferably 8.5 or more.

The specific procedures and various conditions for the above hot tube test are as described in the Example described later.

[Use Application of Lubricating Oil Composition]

The lubricating oil composition of one embodiment of the present invention has excellent efficacy in suppressing deposit formation, detergency, stability, as well as fuel efficiency, regardless of the use environment.

Therefore, the lubricating oil composition of one embodiment of the present invention can be suitably used for lubrication of an internal combustion engine, for example.

Therefore, the lubricating oil composition of one embodiment of the present invention can be applied to various apparatuses that can exhibit the above characteristics, but it can be suitably used for lubrication between parts in an internal combustion engine. Furthermore, among internal combustion engines, it can be more suitably used for lubrication between parts in diesel engines, in particular. In addition, it can also be suitably used for lubrication between parts in a supercharger equipped with an EGR system that re-intakes and recirculates a portion of the exhaust gas.

Such internal combustion engines tend to be under high temperature and/or high pressure environments, which tend to increase the evaporation of the lubricating oil composition and reduce its fluidity, resulting in deposit formation. At the same time, reduced detergency and stability and reduced fuel efficiency also tend to be an issue.

With regard to these issues, since the lubricating oil composition of one embodiment of the present invention has excellent efficacy in suppressing deposit formation, detergency, stability, as well as fuel efficiency, regardless of the use environment, it can be also suitably used in lubrication applications of internal combustion engines which tend to be under such high temperature and/or high pressure environments.

When the aforementioned characteristics of the lubricating oil composition of one embodiment of the present invention are taken into consideration, the present invention can also provide the following [I] and [II].

[I] An internal combustion engine, which is filled with the aforementioned lubricating oil composition of one embodiment of the present invention.
[II] A method for lubricating an internal combustion engine wherein the lubricating oil composition of one embodiment of the present invention is applied to the lubrication of an internal combustion engine.

Examples of the internal combustion engine described in the above [I] and [II] include diesel engines and superchargers equipped with an EGR system that re-intakes and recirculates a portion of the exhaust gas.

As described above, the present invention discloses the following embodiments.

[1] A lubricating oil composition comprising: a base oil (A); and a metal-based detergent (B),

• • wherein a content proportion of heavy fraction (Hf) having 32 or more carbon atoms in the component (A) is 14.0 mass % or more based on the total amount of the component (A),
  • the component (B) comprises an overbased calcium salicylate (B1) with a base number of 100 mg KOH/g or more, and
  • a content proportion of the component (B1) in the component (B) is 35.0 mass % or more based on the total amount of the component (B).
    [2] The lubricating oil composition according to the above [1], wherein a content ratio by mass of the light fraction (Lf) having 21 or less carbon atoms to the heavy fraction (Hf) having 32 or more carbon atoms in the component (A), [(Lf)/(Hf)], is 0.05 or more.
    [3] The lubricating oil composition according to the above [1] or [2], wherein a content proportion of light fraction (Lf) having 21 or less carbon atoms in the component (A) is 1.0 mass % or more based on the total amount of the component (A).
    [4] The lubricating oil composition according to any one of the above [1] to [3], wherein a content of the component (B1) in terms of calcium atoms is 0.01 to 0.80 mass % based on the total amount of the lubricating oil composition.
    [5] The lubricating oil composition according to any one of the above [1] to [4], wherein a content of the component (B) in terms of metal atoms is 0.01 to 1.00 mass % based on the total amount of the lubricating oil composition.
    [6] The lubricating oil composition according to any one of the above [1] to [5], further comprising a viscosity index improver (C).
    [7] The lubricating oil composition according to any one of the above [1] to [6], wherein a kinematic viscosity of the lubricating oil composition at 40° C. is 50.0 mm²/s or less.
    [8] The lubricating oil composition according to any one of the above [1] to [7], wherein a viscosity index of the lubricating oil composition is 130 or more.
    [9] The lubricating oil composition according to any one of the above [1] to [8], wherein an HTHS viscosity of the lubricating oil composition at 150° C. is 2.5 mPa·s or more.
    [10] The lubricating oil composition according to any one of the above [1] to [9], wherein a viscosity grade of the lubricating oil composition is 0 W-20 to 0 W-30, as classified according to SAE J300:2015.
    [11] The lubricating oil composition according to any one of the above [1] to [10], which is used in a diesel engine.
    [12] An internal combustion engine, which is filled with the lubricating oil composition according to any one of the above [1] to [11].
    [13] The internal combustion engine according to [12], wherein the internal combustion engine is a diesel engine.
    [14] A method for lubricating an internal combustion engine, wherein the lubricating oil composition according to any one of the above [1] to is applied to the lubrication of an internal combustion engine.
    [15] The method for lubricating an internal combustion engine according to [14], wherein the internal combustion engine is a diesel engine.

EXAMPLES

Next, the present invention will be described in much more detail with reference to Examples, but the present invention is in no way limited to these Examples. Measuring methods for various properties are as follows.

(1) Kinematic Viscosity and Viscosity Index

The kinematic viscosity and viscosity index were measured and calculated in accordance with JIS K2283:2000.

(2) Ring Analysis

Measurements were made in accordance with ASTM D-3238 Ring analysis (n-d-M method).

(3) Content of Components with Each Number of Carbon Atoms Constituting Base Oil

Using a gas chromatograph (product name: GC-2014, manufactured by Shimadzu Corporation), the content of the components with each number of carbon atoms constituting the base oil was calculated by comparing the chromatogram with a standard sample under the following measurement conditions.

• • Column size: 4 mm×3 mm×1.5 mm (SUS)
  • Column packing material: Silicone OV-1 1.5%, Shinwasorb-S 60/80
  • Standard sample: n-hexane, n-paraffin: C8 to C36 standard sample
  • Gas: He gas, 50 mL/min

(4) Base Number (Perchloric Acid Method)

The base number was measured in accordance with “9. Potentiometric titration method (base number/perchloric acid method)” of JIS K2501 “Petroleum products and lubricants—Determination of neutralization number.”

(5) Content of Calcium Atoms (Ca)

The content was measured in accordance with JPI-5S-38-92.

(6) Weight-Average Molecular Weight (Mw)

Measurements were made using a gel permeation chromatograph (HPLC Model 1260 manufactured by Agilent) under the following conditions and the values measured in terms of standard polystyrene were used.

(Measurement Conditions)

• • Column: Two serially connected “Shodex LF404.”
  • Column temperature: 35° C.
  • Developing solvent: Chloroform
  • Flow rate: 0.3 mL/min

(7) HTHS Viscosity (150° C.)

The HTHS viscosity was measured at 150° C. in accordance with ASTM D4683.

Examples 1 to 6 and Comparative Examples 1 to 6

A base oil and various additives were added and mixed in amounts shown in Tables 1 and 2, thereby preparing each lubricating oil composition. In Examples 1 to 3 and Comparative Examples 1 to 3 shown in Table 1, the viscosity characteristics of the lubricating oil compositions are adjusted to correspond to 0 W-20 as classified according to SAE J300:2015. In addition, in Examples 4 to 6 and Comparative Examples 4 to 6 shown in Table 2, the viscosity characteristics of the lubricating oil compositions are adjusted to correspond to 0 W-30 as classified according to SAE J300:2015.

Details of each component used in the preparation of the lubricating oil composition are as follows.

<Component (A): Base Oil>

• • “Base oil (a-1) “: Base oil classified in Group III of the API base oil categories, kinematic viscosity at 40° C.=7.1 mm²/s, viscosity index=109.
  • “Base oil (a-2) “: Base oil classified in Group III of the API base oil categories, kinematic viscosity at 40° C.=18.4 mm²/s, viscosity index=125.
  • Base oil (a-3) “: Base oil classified in Group III of the API base oil categories, kinematic viscosity at 40° C.=32.7 mm²/s, viscosity index=132.
  • “Base oil (a-4) “: Base oil classified in Group III of the API base oil categories, kinematic viscosity at 40° C.=43.8 mm²/s, viscosity index=143.

<Component (B): Metal-Based Detergent>

• • “Overbased Ca salicylate (1) “: Calcium salicylate with base number=356 mg KOH/g, Ca content=12.5 mass %, corresponds to the component (B1).
  • “Overbased Ca salicylate (2) “: Calcium salicylate with base number=228 mg KOH/g, Ca content=7.9 mass %, corresponds to the component (B1).
  • “Neutral Ca salicylate”: Calcium salicylate with base number=67.4 mg KOH/g, Ca content=2.32 mass %.
  • “Overbased Ca sulfonate”: Calcium sulfonate with base number=305 mg KOH/g, Ca content=11.7 mass %.
  • “Overbased Ca phenate”: Calcium phenate with base number=152 mg KOH/g, Ca content=5.49 mass %.
  • “Neutral Ca sulfonate”: Calcium sulfonate with base number=17 mg KOH/g, Ca content=2.4 mass %.

<Component (C): Viscosity Index Improver>

• • “PMA”: Non-dispersed polymethacrylate with Mw=400,000.
  • “Comb-shaped PMA”: Polymethacrylate-based comb-shaped polymer with Mw=310,000.
  • “Dispersed OCP”: Dispersed polyolefin copolymer with Mw=120,000.

<Other Additives>

• • “Additive mixture”: additive mixture of antioxidant, ashless dispersant, friction modifier, anti-foaming agent, and metal deactivator.

Regarding the lubricating oil compositions prepared, the 40° C. and 100° C. kinematic viscosities, viscosity index, and 150° C. HTHS viscosity were measured or calculated, and the following various measurements and tests were carried out. The results of them are set forth in Tables 1 and 2.

(1) Measurement of Residual Oil Content

Using a container and thermostatic air bath as used in the thermal stability test for lubricating oils specified in JIS K2540, 1 g of sample oil was placed in the container and heated at 200° C. for 20 hours while allowing air to flow into the thermostatic air bath at a flow rate of 10 L/hr, and the residual amount of sample oil after heating was measured. Then, the residual oil content was calculated from the following equation.

Residual ⁢ oil ⁢ content [ % ] = 
 Residual ⁢ amount ⁢ of ⁢ sample ⁢ oil ⁢ after ⁢ heating [ g ] / 
 mass ⁢ of ⁢ sample ⁢ oil ⁢ before ⁢ heating ( = 1 ⁢ g ) × 100

It can be said that the higher the residual oil content is, the better the fluidity under high temperature environments, and the higher the efficacy in suppressing deposit formation of the lubricating oil composition become. In the present Example, the lubricating oil composition was considered to have good fluidity under high temperature environments, and highly effective in suppressing deposit formation when the residual oil content was 25.0% or more.

(2) SRV Test

Using an SRV tester (manufactured by Optimol), the coefficient of friction of each prepared lubricating oil composition was measured under the following conditions. It can be said that the lower the coefficient of friction is, the higher the efficacy in reducing friction, and therefore the better the fuel efficiency of the lubricating oil composition becomes. In the present Example, the lubricating oil composition was considered to have good fuel efficiency when the coefficient of friction was 0.08 or less.

• • Test piece: (a) Disc: SUJ-2 material, (b) Cylinder: SUJ-2 material
  • Amplitude: 1.5 mm
  • Frequency: 50 Hz
  • Load: 400 N
  • Temperature: 40° C.

(3) Hot Tube Test

The hot tube test was performed in accordance with JPI-5S-55-99. Specifically, the hot tube test was carried out by passing the lubricating oil compositions prepared in the Examples and Comparative Examples through a glass tube with an inner diameter of 2 mm at a rate of 0.3 mL/h and air at a rate of 10 mL/min for 16 hours while maintaining the temperature of the glass tube at 290° C. After the hot tube test, the lacquer adhering to the inside of the glass tube was compared to a color chart to rate the degree of color change in the glass tube on a 21-point scale in increments of 0.5, with 10 points for colorless and transparent and 0 points for black. It can be said that the higher the score is, the better the high temperature detergency and high temperature stability of the lubricating oil composition becomes. In the present Example, the lubricating oil composition was considered to have good high temperature detergency when the score was 7.0 or more.

	TABLE 1
	Exam-	Exam-	Exam-	Comparative	Comparative	Comparative
	ple 1	ple 2	ple 3	Example 1	Example 2	Example 3

Composition of	Base oil	Base oil (a-1)	mass %	7.00	—	7.00	7.00	7.00	7.00
lubricating oil		Base oil (a-2)	mass %	66.87	73.87	65.67	76.87	60.67	64.27
composition		Base oil (a-3)	mass %	—	—	—	—	—	—
		Base oil (a-4)	mass %	10.00	10.00	10.00	—	10.00	10.00
	Metal-based	Overbased Ca	mass %	0.52	0.52	0.52	0.52	0.52	0.52
	detergent	salicylate (1)
		Overbased Ca	mass %	1.00	1.00	1.00	1.00	1.00	1.00
		salicylate (2)
		Neutral Ca salicylate	mass %	—	—	—	—	6.20	—
		Overbased Ca sulfonate	mass %	—	—	1.20	—	—	—
		Overbased Ca phenate	mass %	—	—	—	—	—	2.60
		Neutral Ca sulfonate	mass %	0.80	0.80	0.80	0.80	0.80	0.80
	Viscosity index	PMA	mass %	—	—	—	—	—	—
	improver	Comb-shaped PMA	mass %	1.29	1.29	1.29	1.29	1.29	1.29
		Dispersed OCP	mass %	0.12	0.12	0.12	0.12	0.12	0.12
	Other additives	Additive mixture	mass %	12.40	12.40	12.40	12.40	12.40	12.40

Total

mass %

100.00

100.00

100.00

100.00

100.00

100.00

Carbon number	Light	C11 or less	mass %	0.55	0.52	0.46	0.52	0.48	0.50
(C) distribution	fraction	C12-C13	mass %	0.43	0.35	0.45	0.45	0.44	0.47
of base oil	(Lf)	C14-C15	mass %	0.69	0.33	0.71	0.72	0.74	0.73
components		C16-C17	mass %	1.29	0.39	1.29	1.31	1.34	1.33
		C18-C19	mass %	1.76	0.41	1.78	1.79	1.83	1.92
		C20-C21	mass %	2.60	0.87	2.61	2.64	2.76	2.74
	Middle	C22-C23	mass %	5.28	4.09	5.25	5.64	5.60	5.41
	fraction	C24-C27	mass %	35.03	36.93	34.89	39.47	34.80	34.93
	(Mf)	C28-C31	mass %	31.55	34.38	31.55	35.39	31.11	31.18
	Heavy	C32-C35	mass %	13.46	14.35	13.42	10.90	13.07	13.28
	fraction	C36 or more	mass %	7.36	7.39	7.60	1.17	7.84	7.52
	(Hf)

	Total	mass %	100.00	100.00	100.00	100.00	100.00	100.00
Content	Content proportion of light	mass %	7.33	2.87	7.29	7.42	7.59	7.68
proportion	fraction (Lf) of C21 or less
of light,	in base oil
middle, and	Content proportion of	mass %	71.85	75.40	71.69	80.51	71.51	71.53
heavy fraction	middle fraction (Mf) of
in base oil	C22-31 in base oil
	Content proportion of	mass %	20.82	21.73	21.02	12.08	20.91	20.79
	heavy fraction (Hf) of C32
	or more in base off
	Content ratio [light fraction	—	0.352	0.132	0.347	0.614	0.363	0.370
	(Lf)/heavy fraction (Hf)]

Content proportion of overbased Ca	mass %	65.5	65.5	43.2	65.5	17.8	30.9
salicylate based on total amount
(100 mass %) of metal-based detergent
Content of overbased Ca	mass %	0.144	0.144	0.144	0.144	0.144	0.144
salicylate in terms of Ca atoms
Content of metal-based	mass %	0.163	0.163	0.304	0.163	0.307	0.306
detergent in terms of Ca atoms

Properties of	Kinematic viscosity at 40° C.	mm2/s	34.6	36.6	34.2	31.7	38.4	35.5
lubricating oil	Kinematic viscosity at 100° C.	mm2/s	7.4	7.6	7.3	7.0	8.0	7.5
composition	Viscosity index	—	186	182	185	191	187	186
	150° C. HTHS viscosity	mPa · s	2.6	2.7	2.6	2.5	2.8	2.6
Various	Measurement of residual oil	%	28.4	28.5	26.3	19.5	28.7	27.1
measurements/	content (200° C., 20 h)
tests	Residual oil content
	SRV test (40° C.)	—	0.05	0.05	0.07	0.05	0.05	0.09
	Coefficient of friction
	Hot tube test	—	8.5	8.5	8.5	8.5	3.0	5.5
	(290° C.) Score

	TABLE 2
	Exam-	Exam-	Exam-	Comparative	Comparative	Comparative
	ple 4	ple 5	ple 6	Example 4	Example 5	Example 6

Composition of	Base oil	Base oil (a-1)	mass %	6.00	—	6.00	6.00	6.00	6.00
lubricating oil		Base oil (a-2)	mass %	52.48	58.48	51.28	77.48	46.28	49.88
composition		Base oil (a-3)	mass %	25.00	25.00	25.00	—	25.00	25.00
		Base oil (a-4)	mass %	—	—	—	—	—	—
	Metal-based	Overbased Ca	mass %	0.52	0.52	0.52	0.52	0.52	0.52
	detergent	salicylate (1)
		Overbased Ca	mass %	1.00	1.00	1.00	1.00	1.00	1.00
		salicylate (2)
		Neutral Ca salicylate	mass %	—	—	—	—	6.20	—
		Overbased Ca sulfonate	mass %	—	—	1.20	—	—	—
		Overbased Ca phenate	mass %	—	—	—	—	—	2.60
		Neutral Ca sulfonate	mass %	0.80	0.80	0.80	0.80	0.80	0.80
	Viscosity index	PMA	mass %	1.68	1.68	1.68	1.68	1.68	1.68
	improver	Comb-shaped PMA	mass %	—	—	—	—	—	—
		Dispersed OCP	mass %	0.12	0.12	0.12	0.12	0.12	0.12
	Other additives	Additive mixture	mass %	12.40	12.40	12.40	12.40	12.40	12.40

Total

mass %

100.00

100.00

100.00

100.00

100.00

Carbon number	Ligh	C11 or less	mass %	0.26	0.25	0.26	0.26	0.26	0.26
(C) distribution	fraction	C12-C13	mass %	0.30	0.20	0.30	0.28	0.31	0.31
of base oil	(Lf)	C14-C15	mass %	0.77	0.42	0.75	0.75	0.80	0.76
components		C16-C17	mass %	1.41	0.62	1.39	1.38	1.45	1.41
		C18-C19	mass %	2.35	1.18	2.31	2.32	2.34	2.44
		C20-C21	mass %	3.19	1.68	3.13	3.14	3.23	3.27
	Middle	C22-C23	mass %	5.32	4.21	5.26	5.70	5.50	5.34
	fraction	C24-C27	mass %	32.34	33.91	32.18	39.12	31.81	31.92
	(Mf)	C28-C31	mass %	33.34	36.30	33.61	35.29	33.35	33.35
	Heavy	C32-C35	mass %	13.79	14.89	13.89	10.81	13.75	13.97
	fraction	C36 or more	mass %	6.92	6.33	6.92	0.93	7.21	6.97
	(Hf)

	Total	mass %	100.00	100.00	100.00	100.00	100.00	100.00
Content	Content proportion of light	mass %	8.28	4.35	8.13	8.14	8.39	8.45
proportion	fraction (Lf) of C21 or less
of light,	in base oil
middle, and	Content proportion of	mass %	71.01	74.43	71.06	80.11	70.66	70.61
heavy fraction	middle fraction (Mf) of
in base oil	C22-31 in base oil
	Content proportion of	mass %	20.71	21.22	20.81	11.74	20.95	20.94
	heavy fraction (Hf) of C32
	or more in base off
	Content ratio [light fraction	—	0.400	0.205	0.391	0.693	0.400	0.404
	(Lf)/heavy fraction (Hf)]

Content proportion of overbased Ca	mass %	65.5	65.5	43.2	65.5	17.8	30.9
salicylate based on total amount
(100 mass %) of metal-based detergent
Content of overbased Ca	mass %	0.144	0.144	0.144	0.144	0.144	0.144
salicylate in terms of Ca atoms
Content of metal-based	mass %	0.163	0.163	0.304	0.163	0.307	0.306
detergent in terms of Ca atoms

Properties of	Kinematic viscosity at 40° C.	mm2/s	44.7	46.7	43.9	38.4	52.1	46.4
lubricating oil	Kinematic viscosity at 100° C.	mm2/s	9.7	10.0	9.6	8.8	10.6	10.0
composition	Viscosity index	—	211	207	212	219	200	209
	150° C. HTHS viscosity	mPa · s	3.0	3.1	3.0	2.8	3.2	3.0
Various tests	Measurement of residual oil	mass %	32.6	29.1	29.2	21.6	31.2	30.2
	content (200° C., 20 h)
	Residual oil content
	SRV test (40° C.)	—	0.05	0.05	0.07	0.05	0.05	0.09
	Coefficient of friction
	Hot tube test	—	8.5	8.5	8.5	8.5	3.0	5.5
	(290° C.) Score

Tables 1 and 2 indicate that the lubricating oil compositions prepared in Examples 1 to 6 have excellent fluidity even under high temperature environments, and are highly effective in suppressing deposit formation. They also have good viscosity characteristics, such as 40° C. kinematic viscosity, and a low coefficient of friction as measured by the SRV test, which provides excellent fuel efficiency. Furthermore, the hot tube test score was as high as 8.5 or more, and the detergency and stability in high temperature environments were also good.

On the other hand, the lubricating oil compositions prepared in Comparative Examples 1 and 4 have poor fluidity under high temperature environments, which resulted in inadequate suppression of deposit formation. The lubricating oil compositions prepared in Comparative Examples 2 and 5 had a higher 40° C. kinematic viscosity than the Examples in the same table, which resulted in issues with fuel efficiency, low scores in the hot tube test, and issues with detergency and stability in high temperature environments. Furthermore, the lubricating oil compositions prepared in Comparative Examples 3 and 6 had a high coefficient of friction as measured by the SRV test, which resulted in issues with fuel efficiency, low scores in the hot tube test, and issues with detergency and stability in high temperature environments.