Viscosity modifier for lubricating oil and lubricating oil composition

Public can get excellent low-temperature performance of lubricating oil composition for lubricating oil with a viscosity adjusting agent, and incorporating a viscosity regulator and excellent lubricating oil composition for low temperature performance. The viscosity modifiers include: ethylene/propylene copolymer (a), its density is 857-882kg/m3,Mw is 80,000-400,000,Mw/Mn is 2.3 or lower density (D:kg/m3) and melting point (Tm: ℃) meet Tm=1.247xD-1037; ethylene/propylene copolymer (b), the ethylene content is 70-79% (weight), Mw 80,000-250,000 (not including 250,000 ), Mw/Mn for 2.3 or more low, Tm for 15-60 ℃, vinyl content (e: weight%) and melting point Tm (℃) meet relationship 3.44xE-206=Tm; vinyl/propylene copolymer real (c), its vinyl content for 70-79% (weight), Mw for 250,000-400,000,Mw/Mn for 2.3 or more low, Tm for 15-60 ℃, vinyl content (e: weight%) and melting point (Tm: ℃) meet relationship 3.44x E-204＝Tm。 Lubricating oil composition containing ethylene/propylene copolymer (a), (b) and (c) any type of lubricating base oil (d) decline in pour point and selection agent (e) mixture.