| 摘要 |
The present invention is intended to provide a lubricating oil additive having high viscosity index improvability and shear stability and a lubricating oil composition containing the additive and having excellent viscosity index and excellent shear stability. The lubricating oil additive comprises an ethylene/ alpha -olefin random copolymer having the following properties: (i) said copolymer is a copolymer of ethylene and at least one alpha -olefin selected from alpha -olefins of 3 to 20 carbon atoms and contains at least constituent units derived from ethylene in amounts of 10 to 75% by mol and constituent units derived from at least one alpha -olefin selected from alpha -olefins of 8 to 20 carbon atoms in amounts of 20 to 80% by mol, (ii) the kinematic viscosity at 100 DEG C is in the range of 500 to 1,000,000 mm<2>/s, (iii) the intrinsic-viscosity Ä eta Ü is in the range of 0.15 to 1.0 dl/g, (iv) the molecular weight distribution (Mw/Mn), as measured by GPC, is not more than 4, and (v) the number-average molecular weight is in the range of 5,000 to 30,000.
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