compositions and methods are disclosed for reducing combustion chamber deposits and / or intake valve deposits in spark ignition internal combustion engines . a butyrolactam alkoxylate and / or a butyrolactam derivative of this invention or a mixture with at least one additional compound of this invention is added to a liquid hydrocarbon or liquid hydrocarbon - oxygenate gasoline each in an amount of about 0 . 0005 - 0 . 5 wt % of the gasoline . preferably the gasoline is unleaded . the preferred additional components include polyethers and polyisobutylene amine .