For every hour a vehicle is idling — which is when the engine is running but the vehicle is not moving — it it uses an estimated 0.2-0.7 gallons (0.75-2.6 liters) of gas. A common belief is that restarting a car’s engine uses more fuel than idling, but if a car idles for more than 30 seconds, it might be more fuel efficient to turn off the engine. Figures can vary depending on the specific vehicle, fuel cost and usage, but turning off the engine and restarting it instead of idling would save an estimated $70-$650 US Dollars (USD) a year.
More about fuel consumption:
- Diesel trucks waste more fuel when idling, at about 1 gallon (3.79 liters) per hour.
- A study that observed one restaurant drive-through for a total of 54 hours found that 3,756 vehicles idled for five minutes or more.
- The average driver is estimated to let his or her vehicle idle for five to 10 minutes each day.