The present invention relates to compositions containing a detergent composition and an active metal containing compound, where the detergent composition includes a quaternary ammonium salt detergent and optionally an oxygen-containing detergent, and where the active metal containing compound is in the form of a colloidal dispersion, comprising an organic phase, particles of an iron compound in its amorphous form, and at least one amphiphilic agent. These compositions may be used in fuels and provide improved engine performance when such fuels are used, specifically by reducing fuel injector fouling in the engine and/or by improving the regeneration of the engine's particulate exhaust trap.