| 摘要 |
A lubricating oil composition which is excellent not only in low-temperature properties, oxidative stability, lubricity at high temperatures, and energy saving but in low-temperature handleability; and a viscosity modifier for lubricating oils which is used in the lubricating oil composition. The viscosity modifier is characterized by comprising a copolymer of (i) ethylen e, (ii) an a-olefin having three or more carbon atoms, and (iii) a higher a- olefin in which the number of carbon atoms is 4 to 20 and is larger by at least one than that of the a-olefin having three or more carbon atoms, the copolymer being an ethylene/a-olefin copolymer (B) having the following properties (1) and (2): (1) the content of units derived from ethylene (i) i s 40 to 80 wt.%, the content of units derived from the a-olefin having three o r more carbon atoms (ii) is 15 to 59 wt.%, and the content of units derived fr om the higher a-olefin having 4 to 20 carbon atoms (iii) is 0.1 to 25 wt.% (the sum is 100 wt.%) and (2) the weight-average molecular weight (Mw) determined by GPC is 80,000 to 400,000 in terms of polystyrene.
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