| 摘要 |
A method for improving fuel efficiency in an engine lubricated with a lubricating oil by using as the lubricating oil a formulated oil having a composition comprising: a lubricating oil base stock; and a viscosity index improver comprising at least one propylene-based polymer. The at least one propylene-based polymer comprises from 60 wt % to 98 wt % propylene derived units and from 2 wt % to 40 wt % units derived from one or more other alpha olefins, a weight average molecular weight (Mw) as measured by GPC of from 100,000 to 500,000, a number average molecular weight (Mn) as measured by GPC of from 100,000 to 400,000, a molecular weight distribution (MWD=Mw/Mn) of from 1 to 2; and a mole ratio of propylene to one or more other alpha olefins from 50:50 to 85:15.
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