Patent ID: 7183241

Claim:
A lubricating oil composition having extended life as evidenced by reduction in viscosity increase, oxidation and nitration when used in gas engine comprising: (a) a major amount of a base oil of lubricating viscosity; (b) a combination of neutral and overbased metallic detergents in an amount sufficient to provide a sulphated ash in the range of about 0.2 wt % to about 2.0 wt %; (c) based on the volume of the composition from about 0.06 vol % to 0.15 vol % of a zinc dialkyldithiophosphate and about 0.1 vol % to 2.0 vol % of a zinc dialkyldithiocarbamate; and (d) based on the volume of the composition from about 0.5 vol % to about 2.0 vol % of an ashless dihydrocarbylthiocarbamoyl antioxidant.