EPA Issues New MPG Estimate Methods; Estimates Will Likely Drop an Average 8%-12%
12 December 2006
|The new EPA fuel economy sticker. Click to enlarge.|
EPA has issued its final rule on new methods to determine the miles per gallon (MPG) estimates that appear on new vehicle window stickers. The new standards will take effect for model year 2008 vehicles, some of which may be available for sale as soon as next month. EPA proposed the changes in January 2006. (Earlier post.)
Compared to today’s estimates, the city mpg estimates for the manufacturers of most vehicles will drop by about 12% on average, and by as much as 30% for some vehicles. The highway mpg estimates will drop on average by about 8%, and by as much as 25% for some vehicles.
The decreased fuel economy, the EPA took pains to point out, is not a result of a change by the automakers, but in the agency’s methodology for estimating performance.
In vehicles that achieve generally better fuel economy, such as gasoline-electric hybrid vehicles, new city estimates will be about 20 to 30% lower than today’s labels, and new highway estimates will be 10 to 20% lower, according to the EPA.
The nature of current hybrid technology—the addition of a battery as a second source of on-board power, sophisticated control systems, and sometimes a smaller engine—makes a hybrid’s fuel economy more sensitive to certain factors, such as colder weather and air conditioning use.
EPA’s new methods bring MPG estimates closer to consumers’ actual fuel use by including factors such as high speeds, aggressive accelerations, air conditioning use and driving in cold temperatures.
Currently, EPA relies on data from two laboratory tests to determine the city and highway fuel economy estimates. The test methods for calculating these estimates were last revised in 1984, when the fuel economy derived from the two tests were adjusted downward—10% for city and 22% for highway—to more accurately reflect driving styles and conditions.
The city and highway tests are currently performed under mild climate conditions (75° F) and include acceleration rates and driving speeds that EPA believes are generally lower than those used by drivers in the real world. Neither test is run while using accessories, such as air conditioning. The highway test has a top speed of 60 miles per hour, and an average speed of only 48 miles per hour.
Since the mid-1990s, EPA's emissions certification program has required the use of three additional tests which capture a much broader range of real-world driving conditions, including high-speed, fast-acceleration driving, the use of air conditioning, and colder temperature operation (20° F). These conditions affect not only the amount of air pollutants a vehicle emits, but also a vehicle’s fuel economy. However, these tests were not required to measure fuel economy.
Model year 2008 vehicles will be the first to receive the new MPG estimates. Currently, EPA relies on data from two laboratory tests to determine the city and highway fuel economy estimates. The test methods for calculating these estimates were last revised in 1984.
To more clearly convey fuel economy information to consumers, EPA is also enhancing the design and content of the window sticker. The new label will allow consumers to make more informed decisions when comparing the fuel economy of new vehicles. EPA will continue to work with the auto industry, dealers, and other stakeholders, such as the American Automobile Association (AAA), to further educate drivers about all the changes included in the final rule.
In addition to better fuel economy estimates, for the first time, EPA will be requiring fuel economy labeling of medium-duty vehicles, which are between 8,500 and 10,000 lbs., including large sport-utility vehicles and vans. Manufacturers will be required to post fuel economy labels on these vehicles beginning with the 2011 model year.
EPA’s new rule has no impact on the CAFE program, which is administered by DOT’s National Highway Traffic and Safety Administration (NHTSA). CAFE is the required average fuel economy for a vehicle manufacturer’s entire fleet of passenger cars and light trucks manufactured for sale in the United States for each model year. There are separate regulations concerning the test methods and procedures to determine the fuel economy values under the CAFE program.
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