FUEL-ECONOMY LUBRICATION-EFFECTIVE ENGINE OIL COMPOSITION

摘要

Lubricant compositions suitable for use in automotive engines, especially internal combustion engines, the lubricant having a kinematic viscosity at 100° C. of less than 12.5 mm2/s and a high temperature, high shear dynamic viscosity (i.e. at a temperature of 150° C. and a shear rate of 106/s) of at least 2.9 mPa.s, and comprising (a) 70 to 99.5 wt. % of a base oil, preferably a mixture of poly-alpha-olefin and ester, having a kinematic viscosity at 100° C. of 2 to 8 mm2/s and a viscosity index of at least 120, and (b) 0.5 to 3 wt. % of an alkenylarene-conjugated diene copolymer, preferably styrene/butadiene copolymer, as a viscosity index improver. The lubricant provides an improvement in fuel economy performance whilst maintaining effective lubrication of the engine under operating conditions.