Abstract: Use of a lubricating oil composition comprising, or made by admixing, a major amount of oil of lubricating viscosity, and minor amounts of (A) a dispersant additive composition and (B) a detergent additive composition, wherein the oil composition gives a sulfated ash content of at most 1.0 mass %; has a total base number (TBN) of 4 to 9.5; has at least 0.08 mass % of nitrogen derived from the dispersant additive composition, based on the mass of the oil composition; and has at least 25 mmol of soap per 1000 g of the oil composition derived from the detergent additive composition, to improve the cleanliness of pistons in an engine.