Tonengeneral Sekiyu K.k.

Sougawa Yasunori

Katsuya Arai

The present invention provides for a lubricant oil composition for internal combustion engines, that resists oxidation in the presence of NOx and evaporation characteristics, and controls poisoning of a three-way catalyst system for occluding/reducing NOx and formation of deposit in an air intake system. The lubricant oil composition for internal combustion engines, comprises a base oil, which contains aromatic compounds at 1 wt. % or less, sulfur at 10 ppm or less, and paraffin and monocyclic naphthene compounds at 50 wt. % or more as total content, and has a kinematic viscosity of 2 to 50 mm,/s at 100&deg; C. and evaporated quantity of 16 wt. % or less determined by the NOACK evaporation test, wherein the base oil is incorporated with a zinc dithiophosphate at 0.04 to 0.10 wt. % as phosphorus, a calcium phenate and/or calcium sulfonate having a total basic number of 100 to 400 mg KOH/g at 1 to 10 wt. %, and a polyalkenyl succinimide having a boron/nitrogen wt. ratio of 0 to 1.2 and alkenyl group of 1,000 to 3,500 in molecular weight at 0.01 to 0.20 wt. % as nitrogen.

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Saitama-ken, Japan

Sougawa Yasunori