Fuel additives can contribute to maintaining the performance of diesel engines in a variety of ways. This holds true for current and future engine technology.Fouling of indirect injection engines (IDI) has been studied at length. Fouling of direct injection engines (Dl) is less known and less well understood. Problems associated with Dl fouling and a proposed mechanism for it are discussed. Additive effectiveness in preventing injector fouling is confirmed.Injector hole corrosion/erosion, as experienced in the Cummins N14 engine, can be avoided by the appropriate additive chemistry.Particulate traps can also benefit from ashless additive technology aimed at increasing the time between regeneration steps, hence improving effective trap life.