In diesel engines, steel pistons provide significant potential for reducing CO2 emissions in comparison with the aluminum pistons that have been typical up to now. After a long history of positive results in commercial vehicles, MAHLE has therefore developed steel pistons for passenger car diesel engines to the point of series production readiness. Significant advantages result from the frictional loss. Thermodynamic conditions additionally result in advantages in combustion that lead to a reduction in fuel consumption and emissions levels. The lower compression height of a steel piston can also be utilized to increase the swept volume or to decrease the height of the engine.