How much gas does idling waste and what it means for your fuel tank

“Idling” refers to running a vehicle’s engine when it’s not moving, such as when you’re at a red light or stuck in traffic. Idling is part of the process of driving a car and is a common occurrence for most drivers. However, idling may not be the best for your car, fuel consumption, or the environment.

Reducing the amount of time vehicles are idling is a simple way to maintain and even increase fuel economy among fleet vehicles, especially as gas prices rise.

Is idling bad for your engine?

Letting a vehicle idle does more damage to the engine than starting and stopping. In fact, running an engine at low speed (idling) causes twice the wear on internal parts compared to driving at regular speeds¹. 

Excessive idling can also cause a buildup of carbon residue in a truck’s engine. Because the engine is not operating at its optimal temperature when idling, fuel is only partially combusted, leading to fuel residue buildup on the cylinder walls. This can further damage engine components, including spark plugs and exhaust systems, increasing maintenance costs and shortening the life of the engine.

Idling and fuel consumption

Idling vehicles can use more gas than you might realize. This directly affects how much you spend on gas and how often you need to refuel. However, the amount of fuel a vehicle consumes while idling varies depending on factors such as its weight, engine size, and the type of fuel it takes. Some states and local governments even have anti-idling laws that restrict engine idling and impose fines on drivers who violate them.

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 Car idling & non-diesel engines 

Generally, the smaller your vehicle is, the less gas it will use while idling. According to research done by Argonne National Laboratory (Argonne), a compact sedan uses 0.16 gallons of non-diesel fuel per hour of idling with no load². But with average fuel prices at nearly $4.10 per gallon in the U.S. this year, the cost of idling can add up for drivers who spend a lot of time behind the wheel each year.

Truck/semi-truck idling & diesel engines

When heavy-duty trucks idle, even more fuel is wasted than when the average car idles. According to the Department of Energy, heavy-duty trucks consume about 0.8 gallons of fuel per hour when idling. Truck drivers often need to leave their trucks idling during their rest periods, which can be up to 10-hours, which would waste nearly 8 gallons of fuel while they sleep. In addition, non-job-related idling may add to these costs. A 30-minute lunch break for each of your drivers every day could cost you another 2.5 gallons of wasted fuel. Over the course of a year, a long-haul truck could idle for about 1,800 hours, using nearly 1,500 gallons of diesel, which is $5.82 per gallon in the US as of June 2022. For one heavy truck, the cost of idle fuel waste averages about $8,730.

Idling a heavy-duty truck consumes about 0.8 gallon of fuel per hour.³ Semi-trucks and heavy-duty trucks transport most goods consumed in the U.S., so reducing the overall cost of transportation is essential to the economy.

Engine idling and the environment 

Idling and wasted fuel also have a serious environmental impact. Engine idling is particularly bad for air quality, and the World Health Organization estimates that air pollution is responsible for 4.2 million deaths each year. Research conducted by Argonne via the Department of Energy estimates that 11 million tons of carbon dioxide, 55,000 tons of nitrogen oxides, and 400 tons of particulate matter are emitted into the environment from heavy-duty trucks idling during rest periods.

These numbers don’t include the many other hours of idle time from smaller vehicles or the nonproductive idle time that occurs when trucks are loading and unloading. Emissions from engine idling are contributing to climate change and impacting air quality, which poses negative health risks for everyone.

Potential solutions for engine idling reduction 

For many people, reducing the amount of time spent with your engine running is a priority, if not a necessity. For instance, though everyone can benefit from fewer idling cars on the road, business owners who have to manage their fleet of vehicles stand to save money by reducing idling time.

1. For drivers of small vehicles, it is recommended you turn off your engine if you plan to idle for longer than 10 seconds. It is a common myth that restarting your engine uses more gas and causes engine wear.
2. Don’t idle to warm up your engine, start driving instead. The engine will warm up quicker.
3. GPS fleet tracking software is a way to reduce idling in fleets. This software can be used to gather data about what vehicles and drivers are doing, so fleet managers can see if there are ways to improve performance and reduce time spent idling.
4. Train and coach drivers  as a solution to reducing the amount of time spent idling. Coaching should be constant while teaching drivers to avoid idling can help establish best practices early on. Guidelines for engine idling should be part of your training program and safety culture.
5. Fleet managers and individual owner-operators should consider purchasing auxiliary power units (APUs) to reduce engine idle time. APUs can power trucks during rest periods without using fuel so that drivers can enjoy the comforts of their cabins, such as AC and lights, without burning fuel.
   
   

Engine idling may seem harmless, but it has tremendous impacts that negatively affect everyone. It wastes a significant amount of money on fuel and puts harmful toxins into the environment. Keep idling top of mind when you’re driving so that you can do your part to reduce it. 

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¹https://www.epa.gov/dera/school-bus-idle-reduction#:~:text=Engine%20Wear%2Dand%2DTear&text=Fact%3A%20Running%20an%20engine%20at,few%20minutes%20to%20warm%20up.Fact #861 February 23, 2015 idle fuel consumption for selected gasoline and diesel vehicles. Energy.gov. (n.d.). Retrieved June 19, 2022, from https://www.energy.gov/eere/vehicles/fact-861-february-23-2015-idle-fuel-consumption-selected-gasoline-and-diesel-vehicles

²Fact #861 February 23, 2015 idle fuel consumption for selected gasoline and diesel vehicles. Energy.gov. (n.d.). Retrieved June 19, 2022, from https://www.energy.gov/eere/vehicles/fact-861-february-23-2015-idle-fuel-consumption-selected-gasoline-and-diesel-vehicles

³Long-haul truck idling burns up profits - energy. (n.d.). Retrieved June 19, 2022, from https://afdc.energy.gov/files/u/publication/hdv_idling_2015.pdf