Gas mileage vs. temperature

By Steve Schaeber, MACS Technical Editor

Drivers across the US have been enjoying the recently lower prices at the pump which we’ve been seeing now for the past few months. In fact, it seems that week after week the pump price continues to drop by a few cents. That’s great news for those who use their vehicles to commute back and forth to their jobs, especially if it includes a significantly long drive. The savings in fuel can really add up.

Figure 1 - S1860059

But just because oil prices are near 5 year lows, fuel is far from being cheap, and we don’t want to waste it now any more than we did before. Now that much of North America is well into the winter season, the cold weather we’re experiencing has a pretty dramatic effect on our vehicle’s efficiency. In fact, according to the U.S. Department of Energy, a conventional gasoline car’s gas mileage is about 12% lower at 20°F than it would be at 77°F, and it can drop as much as 22% for very short trips of 3 to 4 miles. It might not sound like much, but using a 2006 Chevy Malibu as an example, which usually gets a combined 26 mpg, its mileage can be expected to drop down to between 19 and 23 mpg. Here’s some reasons why:

  • It takes longer for your engine to reach its most fuel-efficient temperature. This affects shorter trips more, since your car spends more of your trip at less-than-optimal temperatures.
  • Heated seats, window defrosters, and heater fans use additional power.
  • Warming up your vehicle before you start your trip lowers your fuel economy—idling gets 0 miles per gallon.

Figure 2 - S1860056

The website  lists some ways to help improve wintertime fuel economy.

  • Park your car in a warmer place, such as your garage, to increase the initial temperature of your engine and cabin.
  • Don’t idle your car to warm it up. Most manufacturers recommend driving off gently after about 30 seconds. The engine will warm up faster being driven.
  • Don’t use seat warmers or defrosters more than necessary.
  • If you drive a plug-in hybrid or electric vehicle, using the seat warmers instead of the cabin heater can save energy and extend range.If you’re a service professional and not a MACS member yet, you should be! Become a member and receive a technical newsletter with information like what you’ve just read in this blog post visit for more information.You can E-mail us at . To locate a Mobile Air Conditioning Society member repair shop in your area. Click here to find out more about your car’s mobile A/C and engine cooling system.

    Mobile A/C professionals should plan to attend 35th annual Mobile Air Conditioning Society (MACS) Worldwide Training Conference and Trade Show, Meet me at MACS Make Connections that Matter, February 5-7, 2015 at the Caribe Royale, Orlando, FL.


About macsworldwide

Mobile Air Conditioning Society (MACS) Worldwide Founded in 1981, MACS is the leading non-profit trade association for the mobile air conditioning, heating and engine cooling system segment of the automotive aftermarket. Since 1991, MACS has assisted more than 600,000 technicians to comply with the 1990 U.S. EPA Clean Air Act requirements for certification in refrigerant recovery and recycling to protect the environment. The Mobile Air Conditioning Society (MACS) Worldwide’s mission is clear and focused--as the recognized global authority on mobile air conditioning and heat transfer industry issues.
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