EPA evaluating how it rates gas mileage for hybrids

• The EPA wants to make sure gas mileage ratings for a new breed of hybrids are realistic
• Is focusing on Ford C-Max%2C which can cruise up to 62 mph on electric power and is rated 47 mpg
• Probe could result in new procedures%2C sticker numbers

The Environmental Protection Agency has launched an evaluation of whether the ways it tests gas mileage give realistic window-sticker ratings for advanced hybrid cars.

The probe centers on a generation of hybrids capable of highway speeds on electric power alone. Chris Grundler, EPA's director of the Office of Transportation and Air Quality, said he wants to be sure the EPA's testing procedures are keeping up with rapidly evolving auto technology.

"This is a different type of hybrid, and we need to understand it," he told USA TODAY in an interview.

The agency's action comes after Consumer Reports wrote that its gas mileage in real-world use of Ford's new C-Max crossover and Fusion sedan hybrids, 37 mpg and 39 overall, respectively, fell far short of their EPA ratings of 47 in mixed driving.

The EPA's evaluation could result in changes in the labeling that EPA requires on cars' window stickers and in consumer information it offers on its website, said Grundler.

One problem, he said, is that the newest hybrids are extra sensitive to driving habits. A hybrid driven aggressively might get far worse gas mileage than its window-sticker rating. "If you drive a hybrid the way you drive your Porsche, you are going to get less (gas mileage) than the national average."

EPA is preparing to test a Ford C-Max in Ann Arbor, Mich. Ford says the C-Max can run up to 62 mph on electric power before the gas engine has to help.

Ford officials are fine with the testing. "We agree with the EPA that hybrid fuel-economy performance industrywide can be more variable compared to conventional vehicles," said spokesman Said Deep. "We are open to working with the agencies to further improve the process for generating fuel-economy labels."

Such EPA testing is not routine. Mileage testing is typically done by automakers, following rules set by the EPA, which then retests about 15% to be sure its procedures are being followed.

Grundler said the evaluation also could include General Motors' Volt plug-in electric with a backup gas engine, but said Volt has not been a source of complaints about ratings not matching real-world results. GM had no comment.

In addition to sometimes leading to owner dissatisfaction, gas mileage ratings are increasingly the subject of lawsuits. Two California law firms are consolidating suits by hundreds of owners of Ford Fusion and C-Max hybrids into a class action.

A potential settlement of lawsuits over several Hyundai and Kia models came before a federal judge in Los Angeles on Thursday. The companies lowered gas mileage ratings on certain models last year on EPA's orders after it was determined that the test results they submitted to the EPA were faulty. Grundler says EPA's investigation into inflated Hyundai and Kia mileage ratings is "ongoing."

Hyundai spokesman Chris Hosford and Kia spokesman Scott McKee each said the companies would not comment regarding ongoing litigation.