DETROIT — Federal regulators are planning changes to vehicle fuel-economy ratings after the Ford Motor Co. said Thursday that it was cutting the miles-per-gallon rating on one of its popular hybrid models.
The Environmental Protection Agency said it would update its labeling rules — which date to the 1970s — to resolve disparities among the growing number of hybrid and electric vehicles on the market.
The move comes as more consumers and analysts are challenging the accuracy of government fuel-economy stickers on new models. At the same time, automakers are pushing to improve fuel economy as strict new government mileage standards are phased in.
In Ford’s case, the automaker said it would reduce the stated fuel economy of its C-Max hybrid utility vehicle to 43 miles per gallon from 47 miles per gallon in combined city and highway driving.
A Ford executive said Thursday that the company was voluntarily reducing the rating, and would offer cash payments to C-Max owners as reimbursement for additional fuel consumption.
Raj Nair, Ford’s head of global product development, said that reducing the rating would allay the concerns of consumers who are not achieving the previously stated fuel-economy number.
“We are taking actions with our popular C-Max hybrid so that customers are even more satisfied with their vehicle’s on-road fuel efficiency performance,” he said.
Ford said it would make a goodwill payment of $550 to any customer who bought the current C-Max model and $325 to consumers who leased one.
Industry analysts said Ford had to address the growing concerns over the reliability of its fuel-economy claims.
“Ford wouldn’t take such a drastic step if it didn’t feel that it was absolutely necessary, even if it’s just to protect its image,” said John O’Dell, green-car analyst at the auto-research site Edmunds.com.
It is not clear how much the consumer campaign will cost Ford, the nation’s second-largest automaker behind General Motors.
The current fuel economy rules specify that automakers can use the same fuel-economy numbers for similar-size vehicles equipped with the same engines and transmissions.
The government requires automakers to test the fuel economy of the biggest-selling model in a specific category. In its midsize hybrid class, for example, Ford tested the Fusion sedan version because it was the top seller.
When the Fusion hybrid achieved 47 miles per gallon in combined city and highway driving, Ford was allowed to apply that rating to the C-Max hybrid as well. But consumers and automotive publications have questioned whether the C-Max hybrid could achieve that rating. Ford also faces several lawsuits that challenge the vehicle’s fuel-efficiency claims.
Nair said that many variables can affect the real-world fuel economy of a hybrid vehicle, including weather conditions and driving behavior. “With hybrids, there is a lot more variability,” he said.
He added that it was difficult to make an exact comparison between the C-Max, a utility vehicle with a chunky design, and the sleeker-looking Fusion passenger car.
Ford expects to improve the C-Max hybrid’s fuel efficiency when a revamped version of the vehicle is introduced at the end of this year.