A method of preventing or reducing the occurrence of Low Speed Pre-Ignition (LSPI) in a direct-injected, boosted, spark-ignited internal combustion engine that, in operation, generates a break mean effective pressure level of greater than about 15 bar, at an engine speed of from about 1500 to about 2500 rotations per minute (rpm), in which the crankcase of the engine is lubricated with a lubricating oil composition containing at least about 0.2 mass % of magnesium sulfated ash.