The GCI combustion engine is a self-igniting petrol engine, so it combines the advantages of a diesel engine with those of a petrol engine. With the GCI engine, part of the hot exhaust is channelled back into the combustion chamber. This causes the temperature to rise sharply, and self ignition occurs under the compression. Through the variable gearbox developed by VW, the valves can be regulated so as to make exhaust gas recirculation possible. Sparkless ignition petrol engines are more economical and cleaner and make new combustion systems possible.