How Can I Better Explain That Things Like Leaving Your Car Running Have Big Impacts?

Ask a Scientist - July 2013

Rani Kokatnur of Lompoc, CA, asks "When I see people sitting in their cars with the engines idling, I think about all that wasted gas. How can I better explain to people that “little things” like leaving your car running in a parking lot really do have big impacts on the environment (and on their wallets)?" and is answered by Dr. David Reichmuth, a senior engineer in the Union of Concerned Scientists’ Clean Vehicles Program.  

There is no doubt that gasoline used while idling in a parking lot is simply wasted. An idling car will use up to a half gallon of gasoline per hour. That means that if you idle your car for just 10 minutes a day while dropping off and picking up kids from school or childcare, you will waste up to 20 gallons of gas over the course of the year. At four dollars per gallon, that’s $80 worth of gas. It’s also equal to roughly 450 pounds of avoidable global warming emissions. So, it’s a good idea to turn off your car’s engine anytime you are out of traffic and won’t be moving for a minute. 

Some people also claim that it’s good for a car’s engine to idle for a while before driving, but today’s cars don’t need to be warmed up. In fact, today’s hybrid cars and some newer non-hybrids now come with technology that turns off the engine automatically when idling, both in parking lots and the shorter stops in traffic. Called “start/stop technology,” this system features a more durable starter motor paired with accessories (like A/C) that are electric powered rather than belt driven, which use the gasoline engine. These systems can reduce a car’s gasoline use by five percent. And, of course, another good way to solve the idling problem is to get rid of the gasoline engine altogether. The motors of electric vehicles run only when needed. Plug-in hybrid electric vehicles like the Chevy Volt have only been widely available for a few years, but the sales are already outpacing the first hybrids so you may soon see more and more people sitting in parking lots without idling at all.

Some other little things that can add up to sizable savings in fuel, money and global warming emissions? Keeping your tires properly inflated can save you anywhere from 5 to 25 gallons of gas per year ($20-$100 per year), depending on the size of your vehicle. Reducing weight and drag (like that empty clamshell on top of your car) can add up to savings too, as can minimizing rapid acceleration and braking. For more such advice that doesn’t take much time or effort but can save you money and trips to the gas station, check out UCS’s handy list of tips. Plus, you’ll find many more practical tips for reducing fuel use in driving (along with other great suggestions for home and travel) in the UCS book Cooler Smarter.

Both driving smarter and using new technologies are part of the UCS Half the Oil plan—a feasible program to cut America’s oil use in half in 20 years through a combination of efficiency and innovation. By cutting our oil use, we can save money, create jobs, protect our health, lower global warming emissions, and establish America as a global leader in transportation technology. You can find the details in our reports, but a great way to share the plan is with our short Half the Oil video.

David Reichmuth is a senior engineer in the Clean Vehicles Program, focusing on oil savings and vehicle electrification. Before coming to UCS, Dr. Reichmuth worked for Sandia National Laboratories in Livermore, California, where he modeled the potential costs and benefits of the large-scale adoption of battery electric, hydrogen fuel cell electric, and improved petroleum-fueled vehicles. Dr. Reichmuth earned his master’s and Ph.D. degrees, both in chemical engineering, from University of California-Berkeley where he investigated biological methods to reduce the sulfur content of fuels.

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