EPA Testing Changes May Impact New Vehicle MPG Ratings

Consumers shopping for a 2017 vehicle may find new models have slightly lower Environmental Protection Agency (EPA) estimated fuel economy compared to 2016 versions of the same cars. The difference is the result of new testing guidelines issued by the EPA in 2015 (to take effect for the 2017 model year) after the agency determined previous procedures could result in automakers overstating vehicle fuel economy.

At the center of the controversy was the EPA "coastdown" test, which calculates the impact of rolling resistance and aerodynamic drag on the vehicle. The coastdown test involves a calculated "road-force load" number that is used when programming a dynamometer to conduct the test. The number will be higher under the new guidelines, and the change is most noticeable in highway fuel economy ratings, although in some cases it may be sufficient to reduce the combined city/highway number as well.

While this change means automakers now have a better understanding of the testing requirements, and posted fuel economy estimates will be more accurate, it also creates some challenges. The automakers' struggle to achieve Corporate Average Fuel Economy requirements is now harder, since fuel economy estimates will be slightly lower. In addition, consumers cannot compare 2017 vehicle fuel economy ratings to those of prior model years, even though the vehicles may be built and perform exactly the same as before.

AAA Impact:

Government/Public Relations – Over the past couple of years, the EPA has taken a number of steps to improve the accuracy of fuel economy labels. In addition to auditing automakers and requiring them to verify results, the agency is also revisiting testing procedures and where necessary making updates. The impetus for re-evaluating the "coastdown" test was the revelation that a handful of automakers had overstated their vehicles' MPG rating, and the above-mentioned updates are designed to standardize test procedures and better align them with what an average driver would experience on the road. 

AAA is also working to provide consumers with up-to-date and accurate information about their vehicle's fuel economy. Working in collaboration with the Automobile Club of Southern California's Automotive Research Center, AAA has released several phases of fuel economy research designed to provide drivers with additional information that will help aid in purchase decisions. AAA will continue to engage with the EPA and other agencies on the subject