Tonengeneral Sekiyu K.k.

Noboru Umemoto

Hiroshi Nakanishi

Heat resistant lubricatant oil compositions consisting of a synthetic lubricating oil composition mainly composed of a polyphenyl ether and so excellent in heat and oxidation resistance and wear resistance as to be suitable for use under severe conditions, particularly, under high-temperature and high-load conditions are disclosed. One embodiment is a lubricating oil composition obtained by mixing, to (a) a base oil consisting of a polyphenyl ether and/or a polyphenyl thioether, (b) an amine-type antioxidant 0.1-0.8 mass %, on the basis of the total mass of the lubricating oil composition, (c) a phosphate 2-3 mass %, and (d) an amine salt of acid phosphate 0.07-0.15 mass %. A second embodiment is a lubricating oil composition obtained by mixing, to (a) a base oil consisting of a polyphenyl ether having 5 aromatic rings and/or its hydrocarbon substituted group, (b) a polyphenyl thioether 0.05-5 mass %, on the basis of the total mass of the lubricating oil composition, (c) an amine antioxidant 0.05-5 mass %, (d) a phosphate 2-3 mass %, and (e) an amine salt of acid phosphate 0.07-0.3 mass %.

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Saitama, Japan

Noboru Umemoto