No, it is not more fuel efficient to leave your car running. Leaving your engine idling wastes fuel and money - in fact, research has shown that leaving the engine running for just 10 seconds can use up as much fuel as restarting your vehicle three times. It also produces more emissions, which contributes to air pollution. Unless you’re stuck in traffic or it’s freezing cold outside, turning off your engine is always the best option. So if you want to save money and help reduce air pollution, make sure to turn off your car when you don’t need it running. It could make a big difference in the long run!