TRUNK PISTON ENGINE LUBRICATING OIL COMPOSITIONS

摘要

PURPOSE: A lubricating oil composition for trunk piston engine is provided to reduce formation of black sludge and precipitation. CONSTITUTION: A lubricating oil composition comprises lubrication viscous oil, a carboxylate-containing detergent, and 0.02-0.12 wt% of one or more zinc dithiophosphates. The carboxylate-containing detergent includes alkyl-substituted hydroxy aromatic carboxylic acid salt. A zinc dithiophosphate has 10 or more total base number. 50% or more of alkyl residue of alkyl-substituted hydroxy aromatic carboxylic acid includes C26-28 alkyl group. A carboxylate-containing detergent includes over-based alkali earth metal salt. The over-based alkali earth metal salt is over-based calcium salt.