Provided are; a lubricating oil composition excellent in fuel saving performance, seizure resistance, wear resistance, fatigue lifetime and shear stability, which contains a base oil (A), an olefin polymer (B) having a number average molecular weight of 1,000 or more and 12,000 or less, and a specific sulfur compound (C) and wherein the content of all sulfur atoms based on the total amount of the composition is 1.2% by mass or more and 2.5% by mass or less; and a lubrication method using the lubricating oil composition.

Provided is an internal combustion engine lubricating oil composition having a major amount of an oil of lubricating viscosity; a combination of alkaline earth metal alkylhydroxybenzoate detergents; at least about 50 to about 500 ppm of boron from a boron containing detergent; a molybdenum containing compound in an amount to provide the lubricating oil composition from about 100 to about 1500 ppm molybdenum; a ZnDTP compound; where the composition comprises magnesium in an amount from about 100 to about 800 ppm, and calcium in an amount from about 500 to about 2000 ppm.

Provided are a lubricating oil composition containing a synthetic oil (1) having a kinematic viscosity at 100 C. of 2.5 mm.sup.2/s or less, and a polymethacrylate (2) having a monovalent functional group containing an oxygen atom in the molecule while having a specific structural unit, which satisfies both high viscosity index and high shear stability, and a lubrication method and a transmission using the lubricating oil composition.

Provided are a lubricating oil composition containing a mineral oil (1) having a kinematic viscosity at 100 C. of 2 mm.sup.2/s or more and less than 2.5 mm.sup.2/s, and a polymethacrylate (2) having a functional group containing an oxygen atom in the molecule while having a specific structural, unit, which satisfies both high viscosity index and high shear stability, and a lubrication method and a transmission using the lubricating oil composition.

The present disclosure relates to lubricant compositions comprising a branched copolymer and methods for making such compositions. Lubricant compositions of the present disclosure comprise an oil and a copolymer and have a high temperature high shear (HTHS) viscosity of about 5 or less, shear stability index (30 cycles) of from about 2% to about 80%, a ratio of thickening efficiency to shear stability index (30 cycles) of from about 1:2 to about 1:30, a kinematic viscosity at 100? C. of from about 3 cSt to about 30 cSt, and a thickening efficiency of about 1 or more. In another class of embodiments, the present disclosure provides a lubricant composition comprising a first and a second copolymers wherein the first copolymer has an ethylene content higher than that of the second copolymer, and wherein at least one of the two copolymers is a long chain branched ethylene copolymer.

A lubricant composition includes a lubricant base oil (A) having a kinematic viscosity at 100 C. of 1 to 10 mm.sup.2/s, and an ethylene/-olefin copolymer (B) in which (B1) the peak top molecular weight is 3,000 to 10,000, (B2) the copolymer shows no melting peak, (B3) the value B is not less than 1.1 and (B4) the kinematic viscosity at 100 C. is 140 to 500 mm.sup.2/s. The lubricant composition has a kinematic viscosity at 100 C. of not more than 20 mm.sup.2/s, a peak top of molecular weight in the range of 3,000 to 10,000, and a weight fraction of components having a molecular weight not less than 20,000 of 1 to 10% relative to all components having a molecular weight not less than the molecular weight that gives the peak top.

Polyalkyl(meth)acrylate based comb polymers with weight-average molecular weights of 700,000 g/mol or greater and number-average molecular weights of 130,000 g/mol or greater can be used to improve the high temperature-high shear performance of lubricant compositions, especially of engine oil (EO) compositions. These polymers can be obtained in a reaction mixture comprising monomers, a dilution oil, and an initiator. The resulting lubricant compositions can have improved kinematic viscosity and high temperature high shear performance.

Provided is a lubricating oil composition, which has low viscosity but also prolonged anti-shudder life without reduction of intermetallic friction coefficient. The lubricating oil composition is characterized in comprising (A) a lubricating base oil, and (C) (C-1) a borated succinimide compound with a mass average molecular weight of 4,000-7,000 and (C-2) a borated succinimide compound with a mass average molecular weight of greater than 7,000-10,000.

The presently claimed invention is directed to poly(meth)acrylate copolymers containing alkyl(meth)acrylate comonomer with branched C17 alkyl group. The invention is further related to lubricating oil compositions comprising poly(meth)acrylate copolymers containing alkyl(meth) acrylate comonomer with branched C17 alkyl group as viscosity index improving component.

Provided is a mineral base oil satisfying the following requirements (I) to (III): Requirement (I): a kinematic viscosity at 100 C. is 2 mm.sup.2/s or more and less than 7 mm.sup.2/s; Requirement (II): a viscosity index is 100 or more; and Requirement (III): a temperature gradient |*| of complex viscosity between two temperature points 10 C. and 25 C. is 60 Pa.Math.s/ C. or less as measured with a rotary rheometer under conditions at an angular velocity of 6.3 rad/s and a strain amount of 0.1 to 100%.

The foregoing mineral base oil can become a lubricating oil composition having desirable low-temperature viscosity characteristics, including low-temperature fuel consumption and low-temperature engine start-up performance, and also having excellent high-temperature piston detergency.