Yes, a car wastes gas when the engine starts. When you turn the key to start the engine, the starter motor draws power from the battery to turn the engine over. This process uses a small amount of gasoline, even if the engine doesn't actually start. In addition, if the engine is cold, it will need to run for a few minutes to warm up before it can operate efficiently. During this time, it will consume more gasoline than it would if it were already warm.
According to the U.S. Department of Energy, idling a car for more than 10 seconds uses more gas than turning the engine off and restarting it. So, if you're going to be stopped for more than a few seconds, it's better to turn the engine off. This will save you gas and money, and it will also help to reduce emissions.
