Fuel compositions for internal combustion engines, comprising a principle amount of a liquid hydrocarbon fuel and an amount, which has a cleaning effect, of at least one propoxylate additive of the formula I ##STR00001## where n is an integer from 10 to 20 and R.sup.1 is straight-chain or branched C.sub.8-C.sub.18-alkyl or C.sub.8-C.sub.18-alkenyl, if required in combination with at least one detergent additive, e.g. a polyalkylamine additive of the formula II R.sup.2--NH.sub.2 (II) where R.sup.2 is a straight-chain or branched polyalkyl radical having a number average molecular weight of from about 500 to about 5000, and fuel additive compositions which contain propoxylates of the formula I and, if required, further additives, such as the aforementioned polyalkylamines of the formula II, as intake valve cleaners.