For years, Consumer Reports has been pressuring the EPA to update fuel-economy test procedures so that automakers couldn’t inflate the numbers. Now, the EPA is considering new validation tests to ensure production cars actually get the fuel economy that manufacturers say they do.
The announcement follows investigations of Hyundai and Ford for producing cars that couldn’t deliver the fuel economy promised on their EPA-approved window stickers.
In 2013, Hyundai agreed to issue free gas cards to 900,000 owners of several 2011-2013 models after it admitted errors in its fuel-economy calculations.
Last month, Ford offered payments to 215,000 owners of six models for similar miscalculations. That action followed an investigation into the fuel economy of the C-Max Hybrid, spurred on by owner complaints and Consumer Reports test findings that revealed the C-Max couldn’t match its claimed 47 mpg EPA fuel-economy rating. (Read "Ford Took Advantage of EPA Loophole Big Enough to Drive a Hybrid Car Through" for more details.)
Our guide to fuel economy shows you how to save at the pump and includes coverage of the most efficient vehicles.
Behind the tests
EPA ratings for window stickers are calculated based on testing by automakers, not by the EPA itself. And calculating those ratings is incredibly difficult and subject to a lot of interpretation. The EPA lacks the resources to audit all automakers’ results, and therefore does so on about 15 percent of cars.
EPA specifications call for tests to be run in a laboratory on a dynamometer—essentially a treadmill for cars—to produce consistent, repeatable results. But that’s not all. To calibrate the dynamometer to mimic realistic friction and wind and road resistance, automakers need to measure other inputs.
Ideally, that is done using a coast-down test, where the car is driven at 65 mph on a straight, level track on a windless day, then allowed to coast to see how far it goes before it stops. But the supply of straight, level test tracks and perfect windless days are limited, so most are done using yet more lab tests of individual factors. The final resistance levels are calculated according to a mathematical formula.
Once those are established, cars are driven on two to five simulated routes on the dynamometer. The two main routes were established in the 1970s. (In some cases, results of the final three routes, created in 2006, are arrived at mathematically.) Then the final fuel-economy results are calculated.
The problems have stemmed from calculating the dynamometer resistance from simulated tests, and from using preproduction and prototype vehicles for these tests. (The hitch with the C-Max Hybrid resulted, in part, from EPA rules allowing automakers to certify fuel-economy results for one model by testing another. In that case, it was the Ford Fusion.)
Redoing test procedures
In a recent Wall Street Journal article, the EPA announced that it is considering revising regulations to require automakers to validate the preproduction results of some vehicles using coast-down tests on models already in production; the agency also said it is closing the loophole allowing automakers to certify a vehicle with results from another.
“We’re trying to get consumers the best fuel-economy label they can get,” says Byron Bunker, the director of the compliance division of the EPA’s Office of Transportation Air Quality.
The EPA also issued a statement saying, “We are not considering creating public roadway test procedures to replace laboratory testing. Rather, EPA is considering requiring automakers to perform supplemental test track audits of production vehicles” to validate some inputs to the laboratory tests. Augmenting EPA’s existing preproduction procedures with post-production audits of real-world factors will help further ensure that the data used in EPA labels accurately reflect the vehicles consumers find on dealer lots.”
The agency is gathering information now and hopes to shape a formal proposal that it will make public next year. After that, the proposal would be open for public comment before becoming final.
Consumer Reports’ own fuel-economy tests show that EPA estimates for certain types of cars have overstated their fuel economy. And while EPA estimates often differ from our own, they aren’t necessarily designed to show the same thing.
For example, where the EPA’s highway test cycles involve a lot of stop and go driving, Consumer Reports’ tests highway fuel economy at a steady 65 mph. Bunker says the EPA test aims to show consumers what they can expect door-to-door on a trip that includes highway driving. Consumer Reports' highway test aims to represent what consumers might get on a long highway vacation trip. Likewise, our city circuit typically results in lower fuel economy. (Learn more about how Consumer Reports tests cars.)
We applaud the EPA’s efforts to validate lab tests in the real world and to make labels as accurate as possible across all types of cars.
—Eric Evarts
Consumer Reports has no relationship with any advertisers or sponsors on this website. Copyright © 2006-2014 Consumers Union of U.S.
