A polymer composition contains a comb-shaped polymer (X) containing the following structural units (a) to (c): (a): a structural unit derived from a short-chain alkyl (meth)acrylate (A) having a short-chain alkyl group having 1 to 5 carbon atoms; (b): a structural unit derived from a long-chain alkyl (meth)acrylate (B) having a long-chain alkyl group having 6 to 32 carbon atoms; and (c): a structural unit derived from a macromonomer (C), a content of the structural unit (a) being 70% by mass or more based on the total structural units of the comb-shaped polymer (X); and a hetero atom-containing base oil (Y). The hetero atom-containing base oil (Y) has a kinematic viscosity at 40? C. of 25 mm.sup.2/s or less.

A sliding member has a sliding surface sliding under a wet condition in which a lubricant oil exists. The sliding surface is coated with a laminate film comprising an upper layer and a lower layer. The lower layer comprises hydrogen-free amorphous carbon (hydrogen-free DLC) and carbon particles dispersed on or in the hydrogen-free DLC. The hydrogen-free DLC has a hydrogen content of 5 atom % or less when the lower layer as a whole is 100 atom %. The upper layer comprises boron-containing amorphous carbon (B-DLC) and has protrusions on a surface side of the upper layer along the carbon particles of the lower layer. The B-DLC has a boron content of 1-40 atom % when the upper layer as a whole is 100 atom %. The protrusions have a particle diameter of 0.5-5 m and exist with a density of 20 protrusions/100 m.sup.2 or more.

Provided are a lubricating oil composition containing (A) a specific amide compound and (B) a metal-based detergent, wherein the content of the metal-based detergent (B) as converted in terms of metal atom is, based on the total amount of the composition, more than 300 ppm by mass and 1,000 ppm by mass or less, and having a high intermetallic friction coefficient and excellent clutch anti-shudder performance; and a lubrication method and a transmission using the composition.

Disclosed is a lubricating oil composition for gear oil, comprising a lubricating base oil having a kinematic viscosity at 40 C. of 140 to 350 mm.sup.2/s, a copolymer of an -olefin and an ester monomer having a polymerizable unsaturated bond, a performance additive containing phosphorus and sulfur, and a poly(meth)acrylate pour-point depressant.

There is disclosed an antifoam component which includes at least one poly(acrylate) copolymer for use in a diesel fuel. Poly(acrylate) polymers prepared by polymerizing a (meth)acrylate monomer comprising C.sub.1 to C.sub.30 alkyl esters of (meth)acrylic acid (multifunctional monomer) are also disclosed. Other poly(acrylate) polymers prepared by polymerizing (i) a (meth)acrylate monomer comprising C.sub.1 to C.sub.4 alkyl esters of (meth)acrylic acid (solubility monomer); (ii) a (meth)acrylate monomer comprising C.sub.5 to C.sub.12 alkyl esters of (meth)acrylic acid (surface tension monomer); and (iii) optionally at least one additional monomer comprising a solubility monomer, a surface tension monomer, a monomer comprising C.sub.1 to C.sub.30 alkyl esters of (meth)acrylic acid (multifunctional monomer), or combinations thereof are also disclosed.

A composition obtained by reacting an O,O-dialkyldithiophosphoric acid with a hydroxyalkyl acrylate or a hydroxyalkyl methacrylate, and reacting the product thereof with a dialkylphosphite provides good antiwear protection.

The present disclosure is directed to a lubricant composition that achieves extended anti-shudder durability without causing a decrease in the metal-to-metal friction coefficient, even when the viscosity of the composition is reduced. A lubricant composition comprises (A) a lubricant base oil, (C) (C-1) a succinimide compound or boronated succinimide compound having a weight-average molecular weight of 4,000 to 7,000, (C-2) a succinimide compound or boronated succinimide compound having a weight-average molecular weight of more than 7,000 to 10,000, and (D) (D-1) an amide-based friction modifier.

A lubricating oil composition including greater than 50 wt. % of a base oil; a reaction product of a hydrocarbyl acid phosphate and a nitrogen containing compound; and an oil soluble hydrocarbyl borate. A method for reducing gear scuffing in a transmission including a step of lubricating the transmission with the above-mentioned lubricating oil composition and a method of operating a transmission including steps of lubricating said transmission with the lubricating oil composition described above and operating the transmission, are also described.

The present invention relates to novel aminobisphosphonate compounds useful as antiwear and/or friction modifier additive components, lubricant additive compositions and lubricant compositions each comprising such compounds, and methods for making and using the same.

The invention provides a lubricating oil composition for automatic transmissions is made such that it comprises proportionately as its main constituents: 60 to 98 mass % as low viscosity base oils being base oils belonging to Groups 2 to 4 of the API (American Petroleum Institute) base oil categories wherein the kinematic viscosity at 100 C. is 2 to 5 mm.sup.2/s (Fischer-Tropsch synthetic oil comprising at least 45 to 80 mass %); 1 to 20 mass % as high-viscosity base oils being metallocene/poly--olefins with a kinematic viscosity at 100 C. of 100 to 600 mm.sup.2/s; and 1 to 20 mass % being a polymethacrylate with a weight-average molecular weight of 10,000 to 50,000. The viscosity index of this composition is not less than 190, the Brookfield viscosity at 40 C. is not more than 5000 mPa.Math.s, the 100 C. kinematic viscosity is 5 to 7 mm.sup.2/s, and the rate of reduction of the 100 C. kinematic viscosity after a KRL shear stability test (60 C., 20 hr) is not more than 3%.