The diesel engine is the prime mover with the highest efficiency and therefore remains the engine with the lowest fuel consumption. Since all the combustion engines use natural resources, it is evident to reduce fuel consumption, to take into account economical and ecological aspects. Since CO2 emission, a gaseous emission which leads to the “Green house” effect, is directly proportional to the fuel consumption, lower fuel consumption is very important.The first fuel efficient 3 litre car (3 lit/100-km) with a diesel engine was introduced. At the same time in Europe the diesel engines have also been making in roads into the high-end passenger car category.In the last 15 years, when one compares the limits imposed by the Euro 0 and Euro III standards, a reduction of 85% of critical diesel emission parameters like NOx and particulates has been achieved in passenger cars as well as heavy duty vehicles.Meanwhile, the Direct Injection (DI) combustion method, which is a traditional prime mover of the heavy duty vehicle, has also been implemented in the passenger car sector. Thereby a 15% reduction of fuel consumption as compared to the IDI engines has been achieved, which means a 30% improvement over gasoline engines.Bosch plays a vital role in the development of diesel engines. Consistent development of diesel fuel injection equipment since the twenties up to the present day has led to a high level of technical maturity . During the first decade, diesel technology was concentrated on improving performance and reducing fuel consumption. Today the focus is on stricter requirement regarding environmental compatibility. In the last ten years Bosch has developed new high pressure fuel injection systems for passenger car engines as well as for truck engines.The new, time controlled injection systems with a highly precise injection quantity and an accurately timed injection-begin, along with a highly developed engine management system have made this rapid development possible.