Use of a tertiary hydrocarbyl amine with C1-to C20-hydrocarbyl residues, the overall number of carbon atoms not exceeding 30, as an additive in gasoline for reducing injector nozzle fouling and modifying friction in direct injection spark ignition engines. A fuel additive composition essentially comprising nitrogen-containing dispersants, carrier oils, the above tertiary hydrocarbyl amines and optionally further friction modifiers. A fuel composition comprising a major amount of gasoline and a minor amount of the above fuel additive composition.