LUBRICATING OIL COMPOSITION FOR SPARK-IGNITION INTERNAL COMBUSTION ENGINE

摘要

The lubricating oil composition for a spark-ignition internal combustion engine according to the present invention is used in a spark-ignition internal combustion engine that comprises a piston having piston rings, with the total per-piston tensile force for the tensile forces applied to the respective piston rings being 30 N or less. The lubricating oil composition is characterized by: comprising a base oil, (A) an organometal additive that includes an alkali metal and/or an alkaline earth metal, and (B) an organozinc additive; the concentration of the (A) component relative to the total amount of the lubricating oil composition being 0.15 mass% or less in terms of the metal content; the concentration of the (B) component relative to the total amount of the lubricating oil composition being 0.15 mass% or less in terms of the zinc content; the product of the concentration (in mass%) of the (A) component and the base number (in mgKOH/g) of the lubricating oil composition being 1.3 or less; the product of the concentration (in mass%) of the (B) component and the acid number (in mgKOH/g) of the lubricating oil composition being 1.2 or less; the NOACK evaporation loss of the lubricating oil composition being 10 mass% or greater; and the kinematic viscosity of the lubricating oil composition being 9.3mm2/s at 100°C. The lubricating oil composition is capable of preventing the deterioration of the combustion state within the spark-ignition internal combustion engine.