Abstract: A trunk piston engine lubricating oil composition comprising (a) a major amount of a base stock comprising at least 90% by weight saturated hydrocarbons; and (b) a minor amount of a base oil having a viscosity index of less than 70 and a cycloaliphatic hydrocarbon content of at least about 25 wt. % is disclosed.

Abstract: A trunk piston engine lubricating oil composition is disclosed comprising (a) a major amount of a base stock containing at least 90% by weight saturated hydrocarbons; and (b) a base stock selected from the group consisting of (i) an ester base stock wherein the ester base stock is present in an amount greater than 10% by weight and no greater than about 45% by weight, based on the total weight of the lubricating oil composition, (ii) an alkylated aromatic base stock, (iii) a base stock having an aromatic content of at least about 50% by weight wherein the base stock having an aromatic content of at least about 50% by weight is not an aromatic extract, and mixtures thereof.