EPA defends its hybrid economy test image

In the wake of Ford Motor Co.’s decision to restate fuel economy estimates on its C-Max Hybrid and the ensuing scandal, the U.S. Environmental Protection Agency (EPA) defends its testing routine.

With owners complaining about worse-than-promised fuel economy and professionals, like Consumer Reports magazine, claiming hybrids felling short of their advertised mpg numbers by 10 percent or more the EPA’s own engineers had no solution but to question the accuracy of their tests, said Christopher Grundler, the agency’s top auto industry regulator.

“This is an industrywide issue with hybrid vehicles,” Raj Nair, the head of global product development for Ford, told reporters this month in announcing the C-Max restatement. “We’ve learned along with EPA that the regulations create some anomalies for hybrid vehicles under the general label rule.”

Still, this summer, when the EPA ran the Toyota Prius and Hyundai Sonata hybrids through the same battery of tests that tripped up the C-Max, the other hybrids did fine. So, according to the EPA, the C-Max had an inflated combined fuel economy estimate of 47 mpg because Ford used test results from the more aerodynamic Fusion Hybrid, which shares a powertrain with the C-Max and weighs about the same.

This was possible due to a decades-old rule allowed that approach to spare automakers the cost of redundant tests on nearly identical cars, such as the old Ford Taurus and Mercury Sable sedans. Now, with cars more efficient and automakers selling more varied models with shared powertrains, the potential to mislead car buyers increased so the rules need to change. Mr. Grundler said it should take the EPA less than a year to propose changes, though the agency has given no timetable for a final rule.