Mercedes is not sitting still in Europe with ever more fuel efficient B-Cla

The moment the clutch is pressed or the brake pedal released, the engine springs back to life almost noiselessly and in a fraction of a second. This ability to restart the engine swiftly yet smoothly gives the ECO start/stop system a key edge over other similar basic systems. To achieve this, Mercedes-Benz fits a starter-generator which is connected to the crankshaft via the belt drive. This allows the engine to start much faster and far more quietly than with the conventional starter. The starter-generator supplies the electrical system as what used to be a separate alternator did previously.