Why YSK: People seem to, on average, think that a car takes a lot of fuel to start up. In reality, it takes on the order of a few millilitres of fuel to start an engine. That means if your car isn’t equipped with an automatic start/stop system to stop your engine instead of idling, it saves fuel to turn off your engine and start it back up when you need it.
Caveat: air conditioning and radio might not work with the engine turned off.
Scenarios where this might be useful include waiting for trains to pass at rail crossings, waiting for food at drive-throughs, dropping off or picking people up on the side of the road when they need to load stuff, etc. May not be a good idea to use this while waiting at a red light because starting the engine does take time which would annoy drivers behind you when the light turns green.
Some cars are equipped with systems that will automatically stop the engine when you are idling for a while (e.g. waiting for a red light). If yours is, then manually turning off your engine will probably result in reduced fuel savings compared to just relying on the car to do it for you.
Yeah new cars usually have the ability to do that themselves and also usually do it when safe.
They auto start when power is needed or if the situation changes. Eg: touch the steering or gas pedal. Another example is my car will auto start it too many cars are around me.
Shutting your non-auto starting car off and then having an emergency happen could land your ass in trouble with insurance and the law. If you’re on the road, your car should be running (unless it was designed this way). Of course people mentioned wear and tear, so that too.
Cheers -Henry