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BACKGROUNDER: Fuel Economy Ratings

Fuel Economy Ratings
Fuel economy is measured under controlled conditions in a laboratory, using a set of tests that are set forth in regulations issued by the U.S. Environmental Protection Agency (EPA).  The test results are used for two purposes:  (1) to establish compliance with the fuel economy and greenhouse gas emissions program; and (2) when combined with additional test results, to provide the estimated fuel economy rating for each vehicle.  These ratings are applied to vehicle window stickers and are published on the government-sponsored website www.fueleconomy.gov.

EPA’s Model Year 2008 and 2011 Label Upgrades
In 2006, EPA issued a new regulation upgrading the way in which vehicle window sticker fuel economy ratings would be generated.  The purpose of the new rule was to update the test procedures to better reflect new technology and the way in which people drive.  The new labels were effective for Model Year 2008.  The new fuel economy ratings were more consistent with the fuel economy many drivers could expect on the roads.

EPA again updated the labels in 2011, this time to reflect the emergence of the new greenhouse gas program and to again account for new vehicle technologies, such as electric vehicles.  EPA also focused on presenting fuel economy information in a format that would be most useful to consumers.

Fuel Economy Labels and Real World Performance
EPA advises that while its ratings are a useful tool for comparing the fuel economies of different vehicles, fuel economy ratings are not fixed numbers.  According to the EPA, fuel economy “varies significantly based on where you drive, how you drive, and other factors.” For this reason, EPA regulations require that every new car be labeled with a window sticker that provides drivers with a range of expected city and highway mileage for most drivers and a clear statement that: “Your actual mileage will vary depending on how you drive and maintain your vehicle.”

EPA has identified several factors that can lower a car’s fuel economy including: aggressive driving; excessive idling, accelerating, and braking in stop-and-go traffic; cold weather; driving with a heavy load or with the air conditioner on; improperly tuned engine or under-inflated tires; use of remote starters; and small manufacturing variations.  Thus, EPA notes that it is “impossible for one set of estimates to predict fuel economy precisely for all drivers in all environments.”

November 2, 2012

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