Commercial vehicles will have to meet increasing requirements in the future with regard to further reductions in emissions and fuel consumption. A holistic view of the subjects, thermodynamics/after treatment of exhaust gases and base engine design/mechanics, is essentially necessary in order to achieve an optimum condition with regard to product and operating costs. In the following report, FEV presents some examples that show, which potentials can still be exploited in the further development of the basic engines of commercial vehicles, one of the more progressive examples being the reduction of the number of cylinders for heavy-duty truck engines from 6 to 4.