Abstract: Disclosed herein is a trunk piston engine lubricating oil composition comprising (a) a major amount of an oil of lubricating viscosity; (b) one or more carboxylate-containing detergents comprising a salt of an alkyl-substituted hydroxyaromatic carboxylic acid, wherein at least about 50% of the alkyl moiety of the alkyl-substituted hydroxyaromatic carboxylic acid comprises C26+ alkyl groups derived from one or more normal alpha olefins; and (c) one or more zinc dithiophosphates in an amount of about 0.02 to about 0.12 wt. % in terms of phosphorus content.