Injector deposits in a direct injection gasoline engine are reduced by providing as fuel for the operation of said direct injection engine a fuel composition comprising a fuel-soluble compound having the formula (I): ##STR00001## wherein R.sub.1 and R.sub.2 are independently C.sub.1-4 alkyl, R.sub.3 is a radical of the formula C.sub.mH.sub.2m wherein m is an integer of 2 to 6, R.sub.4 and R.sub.5 are each independently (i) hydrogen (ii) C.sub.1-4 alkyl, ##STR00002## wherein R.sub.6 is selected from the group consisting of hydrogen and C.sub.1-4 alkyls and R.sub.7 is selected from the group consisting of hydrogen and C.sub.1-30 alkyl, (iv) ##STR00003## wherein R.sub.8 is a saturated or unsaturated, linear, branched or cyclic, C.sub.7-23 hydrocarbyl group or (v) wherein R.sub.4 and R.sub.5 together with the nitrogen atom to which they are bonded, form a cyclic ring in which further hetero atoms.