With the high prices for petrol and diesel, it is advisable to drive your car as economically as possible. One measure is to switch off the engine at traffic lights. But is this really good for the vehicle and fuel consumption?
Economical driving can certainly save a not inconsiderable amount of petrol or diesel. This includes, for example, switching off the engine at a red traffic light. However, it cannot be said in general whether this makes sense. “When it’s worth turning the ignition key varies from vehicle to vehicle and also depends on the vehicle’s age and engine size,” explains Thomas Schwarz from ADAC Südbayern to the online portal “Chip”.
If the traffic light phase lasts more than 30 seconds, you can actually save fuel by switching off the engine. However, if the engine is not yet at operating temperature, it is not advisable to switch it off. This increases fuel consumption and pollutant emissions.
In addition, repeated cold starts in older vehicles can have a negative effect on the car battery: its service life can be reduced, so that the car suddenly no longer starts or breaks down.
Drive sparingly: switch off the engine at around 80 to 90 degrees
Arnulf Thiemel from the ADAC Technik Zentrum gives a guideline: “As soon as the pointer for the coolant temperature is in the middle, i.e. the coolant has reached around 80 to 90 degrees, drivers can use the trick.”
But be careful: If you switch off the engine manually, you should make sure to set the key to ignition stage 2. Important functions such as brake lights, windscreen wipers and windscreen blowers remain activated. The deactivation of the former can ultimately lead to a rear-end collision caused by vehicles approaching from behind.
Technology of the automatic start-stop system depends on certain factors
But what about modern vehicles that have a start-stop system? The technology only switches on here if the battery voltage and the outside temperature are not too low and the engine has reached operating temperature.