The present invention provides a grease composition or a lubricating oil composition which is capable of effectively preventing hydrogen brittleness-caused peeling from occurring on a rolling surface of a rolling bearing, is excellent in durability in a high temperature and speed operation, and can be used for a long time. A grease-packed bearing (1) has an inner ring (2), an outer ring (3), and a plurality of rolling elements (4). A sealing member (6) for sealing a grease composition (7) is provided at openings (8a) and (8b) disposed at both axial ends of the inner ring (2) and the outer ring (3). The grease composition (7) includes a base grease composed of a base oil and a thickener and an additive added to the base grease. The additive contains at least one compound selected from among plant-derived polyphenolic compounds and compounds formed by decomposition thereof. The above-described compounds include tannin, gallic acid, ellagic acid, chlorogenic acid, caffeic acid, curcumin, quercetin, and quinic acid.

The present invention provides a grease composition or a lubricating oil composition which is capable of effectively preventing hydrogen brittleness-caused peeling from occurring on a rolling surface of a rolling bearing, is excellent in durability in a high temperature and speed operation, and can be used for a long time. A grease-packed bearing (1) has an inner ring (2), an outer ring (3), and a plurality of rolling elements (4). A sealing member (6) for sealing a grease composition (7) is provided at openings (8a) and (8b) disposed at both axial ends of the inner ring (2) and the outer ring (3). The grease composition (7) includes a base grease composed of a base oil and a thickener and an additive added to the base grease. The additive contains at least one compound selected from among plant-derived polyphenolic compounds and compounds formed by decomposition thereof. The above-described compounds include tannin, gallic acid, ellagic acid, chlorogenic acid, caffeic acid, curcumin, quercetin, and quinic acid.

The lubricating oil composition of the present invention contains, together with a base oil, a viscosity index improver (A) including a comb-shaped polymer (A1), a detergent dispersant (B) including an alkali metal borate (B1) and an organometallic compound (B2) containing a metal atom selected from an alkali metal atom and an alkaline earth metal atom, and a friction modifier (C) including a molybdenum-containing friction modifier, with the total content of an alkali metal atom and an alkaline earth metal atom being 2,000 mass ppm or less. The lubricating oil composition of the present invention has excellent detergency, fuel saving properties, and LSPI-preventing properties.

The lubricating oil composition of the present invention contains, together with a base oil, a viscosity index improver (A) including a comb-shaped polymer (A1), a detergent dispersant (B) including an alkali metal borate (B1) and an organometallic compound (B2) containing a metal atom selected from an alkali metal atom and an alkaline earth metal atom, and a friction modifier (C) including a molybdenum-containing friction modifier, with the total content of an alkali metal atom and an alkaline earth metal atom being 2,000 mass ppm or less. The lubricating oil composition of the present invention has excellent detergency, fuel saving properties, and LSPI-preventing properties.

An overbased sulfonate modified lithium carboxylate grease composition and method of manufacture comprising overbased calcium sulfonate, overbased magnesium sulfonate, or both added to a source of lithium hydroxide, base oil, and optionally one or more acids when a complex grease is desired. When overbased sulfonate is added, the amount of dicarboxylic acid relative monocarboxylic acid may be reduced. Additionally, the amount of lithium hydroxide added may be less than stoichiometrically needed to react with the acids. A sulfonate modified lithium grease with improved thickener yield and dropping point may be made without multiple heating and cooling cycles or using a pressurized kettle.

Lubricating oil compositions may include a base oil, a succinimide compound, and a thioheterocyclic compound. Such compositions may have a sulfur content of 0.10 mass % to 1.00 mass % based on a total amount of the composition. A phosphorus content represented by P in mass % and a sulfated ash content represented by M in mass %, based on the total amount of such compositions, may satisfy any of conditions A to C: condition A: P<0.03, and M<0.3; condition B: P<0.03 and 0.3≦M≦0.6; and condition C: 0.03≦P≦0.06 and M<0.3.

Lubricating oil compositions may include a base oil, a succinimide compound, and a thioheterocyclic compound. Such compositions may have a sulfur content of 0.10 mass % to 1.00 mass % based on a total amount of the composition. A phosphorus content represented by P in mass % and a sulfated ash content represented by M in mass %, based on the total amount of such compositions, may satisfy any of conditions A to C: condition A: P<0.03, and M<0.3; condition B: P<0.03 and 0.3≦M≦0.6; and condition C: 0.03≦P≦0.06 and M<0.3.

A lubricating oil composition is provided which comprises (a) greater than 50 wt. % of a base oil of lubricating viscosity; and (b) 0.1 to 40 wt. % of an overbased alkaline earth metal alkyl-substituted hydroxyaromatic carboxylate, wherein the alkyl substituent is a residue derived from an isomerized alpha-olefin having from 12 to 40 carbon atoms, and having a TBN, on an actives basis, of less than 600 mg KOH/g, as determined by ASTM D 2896; wherein the lubricating oil composition is a monograde lubricating oil composition meeting specifications for SAE J300 revised January 2015 requirements for a SAE 20, 30, 40, 50, or 60 monograde engine oil, and has a TBN of 5 to 200 mg KOH/g, as determined by ASTM D2896.

A method for improving low temperature performance of a lubricant in a compression-ignited internal combustion engine is disclosed. The method comprises operating the engine with a monograde lubricating oil composition comprising (a) a major amount of a base oil of lubricating viscosity; and (b) a minor amount of an overbased alkaline earth metal salt of an alkyl-substituted hydroxyaromatic compound, the alkyl substituent being a residue derived from an isomerized alpha-olefin having from 12 to 40 carbon atoms per molecule.

The present invention provides a poly(meth)acrylate-based viscosity index improver comprising a core portion and three or more arm portions, wherein each of the arm portions consists of a polymer chain comprising a structural unit represented by the following formula (1), and one end of the polymer chain is bonded to the core portion, and wherein a weight-average molecular weight Mw is 100000 or more, and a ratio of the weight-average molecular weight Mw to a number average molecular weight Mn, Mw/Mn, is 1.6 or less. ##STR00001## [R.sup.1 represents hydrogen or a methyl group, and R.sup.2 represents a C1 to C36 alkyl group.]