It may come as a surprise, but automakers are actually the ones who produce the all-important fuel economy figures displayed on window stickers. The reason the numbers are “EPA-certified” is because they are calculated using standardized methodology developed by the Environmental Protection Agency. Essentially, the engines are hooked up to a dynamometer and programmed to run through a series of varying loads to replicate city and highway driving. After the figures are published, the EPA tests roughly 15 percent of them for verification. Consumer Reports found that the official estimates are actually very accurate when compared to its own standardized, real-world testing results, deviating just 2 miles-per-gallon (MPG) in either direction.
However, Consumer Reports raised red flags after testing the Ford Fusion Hybrid and Ford C-Max Hybrid. While both vehicles were praised for their efficiency, they fell inexcusably short of their reported MPG. Both cars are rated at 47 MPG across the board, but the Fusion Hybrid returned “just” 35/41/39 MPG (city/highway/combined), and the C-Max returned 35/38/37 MPG—differences hovering around 20 percent. Consumer Reports said the discrepancies for “combined” MPG are the two most egregious for any current model. The EPA has been made aware of the issue, though Ford released a statement essentially saying it would stand by its numbers.
Interestingly, these aren’t the only hybrids whose quoted fuel economy doesn’t stack up in the real world. Consumer Reports (see link above) shows that “combined” MPG for the Toyota Prius C Two and Toyota Prius were off by 7 and 6 MPG, respectively. The Honda Civic Hybrid and Infiniti M35h were both down by 4 MPG. So, what’s going on? Though it could be that EPA’s particular testing regime plays to the inherent strengths of hybrid powertrains, it’s just as likely (maybe even more so, as hypothesized by Dan Neil) that some hybrids are calibrated to do well under EPA’s testing process.
If the problem continues, the EPA has two options: revamp its testing procedures, or release a new window sticker that says, “Your results may vary…greatly.”
Image: © Ford Motor Company