When the car is at a standstill, the engine does not need to be running and therefore does not need to consume fuel. Recognition of this essentially simple fact is behind the ECO start/stop function, which is available for the first time in the Mercedes-Benz CLS-Class with the 7G-TRONIC PLUS automatic transmission. In order to implement the auto start and auto stop function with a very high level of comfort in a Mercedes-Benz, it has been necessary to develop complex control logistics and a series of new or modified components, such as a Hall sensor for the crankshaft and a high-output starter motor. That's because Mercedes drivers should only really notice the forced breaks taken by the engine when they are at the filling station - thanks to consumption figures which are up to eight percent lower in urban traffic and five percent lower in the ECE consumption cycle. In the case of the CLS 250 CDI BlueEFFICIENCY, CLS 350 BlueEFFICIENCY and CLS 500 BlueEFFICIENCY models, the ECO start/stop system is fitted as standard. More details can be found in the section "Under the microscope: ECO start/stop function".