Viscosity modifier for lubricating oil and lubricating oil composition

A objective of the present invention provides a lubricant oil composition, comprising a purified low-temperature properties, wherein the oxidation, wherein the temperature of lubricant and fuel electrode, and a low-temperature workability, the invention also provides can be used to the lubricating oil composition a lubricating oil viscosity adjusting agent. The lubricant oil the viscosity adjusting agent comprises ethylene/α - olefin copolymer (B), the copolymer comprising: (i) ethane, (ii) with 3 or more carbon atoms α - olefin, (III) comprises 4-20 carbon atoms α high - olefin, (iii) carbon atom number of more than 1 (II) or more of; and ethylene/α - olefin copolymer (B) is of (b-1) and (b-2): performanceb-1 (a) to (i) content is 40-80 weight percent, comprising 3 or more carbon atoms α of the olefin (ii) content of 15-59 by weight, comprising 4-20 carbon atoms high - α the olefin (III) content of 0.1-25 weight percent, the premise of the total amount of 100 by weight,A b-2 (a) according to weight average molecular weight of polystyrene is GPC by weight of 80,000-400,000.