Environmental protection and health are key issues in today's world. This is borne out by the on-going discussions on climate change und the threat to mankind and the environment posed by combustion-engine exhaust emissions. The increasing volume of traffic is a major challenge for society at large. The results are manifold and include two crunch requirements for the design of the combustion engines of today and tomorrow, namely eco-compatibility and efficiency. As far as environmental considerations are concerned, there is a critical debate focused primarily on the carbon dioxide (CO2) and the soot-particle and nitrogen-oxide emissions of vehicles and engine-driven machinery.