Since harmful nitrogen oxides (NOx) are mainly produced at high temperatures and pressures, it is possible to reduce the NOx concentrates emitted to the environment by up to 50%. On diesel engines, the formation of soot particulates is lowered by approximately 10%. Exhaust gas recirculation is only activated at defined operating points. On petrol engines this is normally the case above idling and up to upper part load, on diesel engines up to approx. 3000 rpm and medium load.