If the engine is off, no fuel is consumed. The start-stop system makes the drivers use this circumstance - but not in any weather.
Question: The start-stop system of my car has worked great in the past. However, it has not worked since the winter. How can that be?
Antwort von Hans-Georg Marmit, automotive expert of the expert organization KÜS: The start-stop system provides, especially in city traffic for lower consumption and less air pollution. If you stand idle and hold down the brake pedal, the electronics will stop the engine and throw it back up as fast as the car goes on. During the service life, be it at traffic lights or in a traffic jam, no fuel is consumed.
An engine stop is not always useful. For example, if the engine has not reached its operating temperature, it is completely counterproductive. And even with low voltage in the starter battery, an engine stop may hurt more than it uses. For the same reason, the automatic start-stop system stops working in extreme cold, because in winter the battery is already under stress anyway. The lower temperature limit varies from manufacturer to manufacturer, usually in the range of plus three to minus five degrees.
The engine will continue to run if the current demand is too high. In summer, for example, the air conditioning and, in the winter, window and seat heating prevent the electronics from switching off the combustion engine. It can also happen in such cases that the engine initially goes out, but after some time but starts again to ensure the cooling. Last but not least, the start-stop system deactivates all indications that the driver wants to park rather than wait. For example, when the buckle is loosened or the door is opened. Even an open bonnet can prevent the engine from stopping.