| abstract |
The lubricating oil composition contains a base oil; (A) an acidic alkyl phosphate ester having a C6 to C20 alkyl group; (B) a dialkylamine and/or a trialkylamine; and (C) (c-1) a sulfur compound in an amount of 0.2 to 0.6 mass% as reduced to S, the sulfur compound containing no poly-sulfur bond which is equal to or longer than -S-S-S- in a molecule thereof and having an S content of the molecule of 15 mass% or more and (c-2) an optional thiophosphoric acid trihydrocarbyl ester in an amount of 0.1 to 1.0 mass%, the ester being represented by formula (I): n n (R-O-) 3 P=S (I) n n(wherein R represents a C6 to C20 hydrocarbyl group) and having a P content of the composition of 150 to 500 ppm by mass n The lubricating oil composition has excellent anti-seizure performance, excellent anti-fatigue performance (e.g., anti-FZG-micropitting performance), and reduced sludge formation in an oxidation test. |