Abstract:
PURPOSE: An engine adjuvant for a gasoline engine lubricant is provided, which is improved in the compatibility with an already-existing lubricant and forms the protection layer on an internal combustion engine easily for preventing the damage of the internal surface of an engine, improving the gasoline mileage and reducing the smoke. CONSTITUTION: The engine adjuvant comprises 50-90 wt% of a synthetic oil mixture of a poly(α-olefin) and a diester oil; 2-15 wt% of a molybdenum compound containing no phosphorus; 2-10 wt% of an oil-soluble secondary amine antioxidizing agent; 2-10 wt% of an alkali earth metal sulfonate; and 2-10 wt% of an ashless imide-based dispersant. Preferably the α-olefin has a viscosity of 15-40 cSt at 40 deg.C and 3-8 cSt at 100 deg.C; the diester oil has a viscosity of 20-40 cSt at 40 deg.C and 3-8 cSt at 100 deg.C; the molybdenum compound is molybdenum carbamate or an organic molybdenum compound; the oil-soluble secondary amine antioxidizing agent is represented by R'N(-R")H, wherein R' and R" are an aryl group of C6-C30; the alkali earth metal sulfonate is a metal alkylbenzene sulfonate represented by the formula 2, wherein R is an alkyl group of C8-C20 and M is a metal element; and the ashless imide-based dispersant is at least one selected from the group consisting of a polybutene-maleic acid ester copolymer, a substituted succinimide, a polyamide succinimide, a polyhydroxy succinic acid ester and a substituted Mannich base.