Idemitsu Kosan Company, Limited

Hidenori Torii

Shinji Aoki

Provided is a lubricating oil composition containing a base oil (A) and an amine-based antioxidant (B), wherein the component (B) contains a phenyl-naphthylamine (B1), an alkylphenyl-naphthylamine (B2) and a di(alkylphenyl)amine (B3), the content of the component (B1) is 2.0 to 10.0% by mass relative to 100% by mass of the total amount of the component (B), the content of the component (B2) is 40.0 to 90.0% by mass relative to 100% by mass of the total amount of the component (B), and the content of the component (B3) is 8.0 to 50.0% by mass relative to 100% by mass of the total amount of the component (B). The lubricating oil composition maintains excellent oxidation stability even in long-term use in high-temperature environments, and has an excellent lifetime and is excellent also in a sludge preventing effect.

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Kisarazu, Japan

Hidenori Torii