The present invention aims to provide a viscosity index improver composition and a lubricating oil composition having a low HTHS viscosity at 100° C., an excellent shear stability, and an excellent low temperature viscosity. The present invention relates to, for example, a viscosity index improver composition (C), containing: a copolymer (A) containing a polyolefin-based monomer (a) represented by the following formula (1) as a constituent monomer; a copolymer (B) containing a (meth)acrylic acid alkyl ester (c) having a C12-C15 straight-chain or branched alkyl group and a (meth)acrylic acid alkyl ester (d) having a C16-C20 straight-chain or branched alkyl group as constituent monomers; and a base oil, wherein a weight average molecular weight ratio {(A)/(B)} of the copolymer (A) to the copolymer (B) is 2 to 55, and a weight ratio (A/B) of the copolymer (A) to the copolymer (B) constituting the viscosity index improver composition (C) is 5 to 100: ##STR00001##

The grease composition including: a base oil having a kinematic viscosity of 5 to 30 mm.sup.2/s at 100° C., a thickener, a polymer having a weight average molecular weight of 1,000 to 500,000, and an aliphatic amide compound. The grease composition is used for sliding between a metal member and a resin member, and capable of reducing friction between them.

The grease composition including: a base oil having a kinematic viscosity of 5 to 30 mm.sup.2/s at 100° C., a thickener, a polymer having a weight average molecular weight of 1,000 to 500,000, and an aliphatic amide compound. The grease composition is used for sliding between a metal member and a resin member, and capable of reducing friction between them.

An additive composition contains a viscosity index improver and a pour point depressant. A process can be used for preparing the additive composition. The additive composition can be used as a lubricant additive in a lubricating oil formulation, and lubricating oil formulations can contain the additive composition.

An additive composition contains a viscosity index improver and a pour point depressant. A process can be used for preparing the additive composition. The additive composition can be used as a lubricant additive in a lubricating oil formulation, and lubricating oil formulations can contain the additive composition.

The invention relates to acrylate-olefin copolymers and to a method for preparing these polymers. The present invention is also directed to lubricant compositions comprising these copolymers, and to the use of these copolymers as a lubricant additive or a synthetic base fluid in a lubricating oil composition, preferably in a gear oil composition, a transmission oil composition, a hydraulic oil composition, an engine oil composition, a marine oil composition, an industrial lubricating oil composition or in grease.

The invention relates to acrylate-olefin copolymers and to a method for preparing these polymers. The present invention is also directed to lubricant compositions comprising these copolymers, and to the use of these copolymers as a lubricant additive or a synthetic base fluid in a lubricating oil composition, preferably in a gear oil composition, a transmission oil composition, a hydraulic oil composition, an engine oil composition, a marine oil composition, an industrial lubricating oil composition or in grease.

The invention relates to a poly alkyl(meth)acrylate polymer comprising polybutadiene-based monomer units and a process for preparing the same. The invention also relates to the use of said polymer as a viscosity index improver in lubricant formulation and to lubricant compositions comprising said polymer.

The invention relates to a poly alkyl(meth)acrylate polymer comprising polybutadiene-based monomer units and a process for preparing the same. The invention also relates to the use of said polymer as a viscosity index improver in lubricant formulation and to lubricant compositions comprising said polymer.

A lubricating oil composition for a transmission, the composition including: (A) a lubricant base oil comprising a mineral base oil and/or a synthetic base oil; and (B) a poly(meth)acrylate having a weight average molecular weight of no more than 25,000, wherein the composition has a kinematic viscosity at 100° C. of 2.5 to 4.9 mm.sup.2/s.