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CARS
Detroit, MI

Getting the MPG claimed for your car is tough

Alisa Priddle
Detroit Free Press
The window sticker displays the mileage ratings for a 2007 Prius hybrid sedan at a Toyota dealership inCentennial, Colo., on Feb. 25, 2007.
  • Hyundai%2C Kia ordered to lower mileage claims on 13 models
  • Ford reduces claimed mileage for C-Max hybrid
  • Vehicle condition%2C driving style%2C road conditions can affect mileage

DETROIT -- Advice for shoppers who want to buy a fuel-efficient car: Use the fuel economy window sticker as a guide, not gospel.

Few drivers achieve the combined miles per gallon on the sticker for a variety of reasons that relate to the U.S. Environmental Protection Agency's test, the vehicle and the driver.

The EPA figures are helpful, but buyers should not feel remorse when they can't duplicate the advertised results in real world driving, analysts say.

The discrepancy can be confusing and frustrating to the point that unhappy consumers have launched lawsuits against automakers. The situation has grown worse after recent high-profile cases where automakers have been forced to drop or modify some of their claims.

Last year, Hyundai and Kia were ordered to lower mileage claims on 13 models after admitting mistakes were made in tests conducted in South Korea. While the EPA establishes the tests, automakers test their own vehicles and submit the results. The EPA spot checks about 15% of them.

Last month, Ford trimmed its claim for the C-Max hybrid from 47 mpg to 43, after acknowledging it didn't test the car's fuel economy. The EPA's "general label" rule allows automakers to test the best-selling vehicle and apply the results to other models with the same weight, engine and transmission. Ford tested the Fusion hybrid sedan and applied the 47 mpg results to the boxier C-Max.

Unhappy customers have sued Ford over the discrepancy. Honda faced lawsuits from disgruntled owners of the 2006 Civic, but in one case a court decided the blame fell on the EPA, not Honda.

"People get more upset when hybrid numbers are wrong because they bought a hybrid for the fuel economy," said analyst Dave Sullivan of AutoPacific.

Toyota made a point of testing the larger Prius V and the smaller Prius c separately from the Prius liftback, even though it could have applied the general label rule, said Bob Carter, senior vice president of Toyota Motor Sales.

"I hate it," Carter said of the continued controversy over EPA figures. "The industry is cast under one shadow. It's not good for the industry to have consumers doubt the information."

Edmunds.com analyst John O'Dell said many consumers don't pay much attention to the EPA figure and many know they are unlikely to achieve the advertised number. But that doesn't mean the certification doesn't have value.

"A car rated at 30 mpg will do better than one rated at 25 no matter how you drive both cars. Consumers can use the ratings as a comparison but shouldn't think it's an implied guarantee that you'll get EPA rating," O'Dell said.

When the government began testing in 1975, highway speed limits were 55 mph and vehicles had regular gasoline engines with less horsepower and torque than today.

The dynamometers in the labs that measured the speed of the wheel spin were incapable of mimicking and handling the acceleration of today's vehicles. They simulated driving conditions on more orderly and less crowded highways and assumed drivers spent 55% of their time on city roads when today, most commuters head immediately for a highway ramp.

Modern technology like air-conditioning, hybrids with regenerative braking and engines that turn off at stops were causing the gap between lab and real-life results to grow again. That prompted a second math correction in 2008 that factored in higher speeds, hot and cold weather and air-conditioning.

"The 2008 modifications did not go far enough but have come a lot closer," said Eric Evarts, auto editor with Consumer Reports.

The next step is to close the general label loophole, at least for hybrids, Evarts said. An EPA spokeswoman said the agency will develop new procedures calling for different labels, according to a vehicle's design.

Consumers need to be aware that a single vehicle can have three sets of results. The 54.5 mpg average fuel economy that automakers must achieve by 2025 translates to about 38 mpg under the EPA formula. In actual driving, the result can vary as much as 9 mpg on the road, depending on the individual driver, vehicle and conditions, O'Dell said.

"If you are a Casper Milquetoast driver and hyper-miler, the last through an intersection and always driving below the speed limit, you could get really close," O'Dell said. "The rule of thumb is to take 10% off the sticker for a gasoline engine and 20% off for hybrids."

Mileage is affected by the condition of your vehicle. Extra occupants and cargo, sticky performance tires and a luggage rack or a bike rack can affect aerodynamics. A boxy vehicle can reduce efficiency up to 15%. Turning on the air-conditioning can lop off another 14%.

Outside temperature and terrain make a difference.

"Laws of physics say I will never get EPA" fuel economy, said O'Dell, who lives at the top of a hill in Southern California."

Increased stop-and-go driving could reduce fuel efficiency 27%, according to Edmunds researchers David Greene and Zhenhong Lin at Oak Ridge National Laboratory in Tennessee. Aggressive drivers can expect 18% lower economy with frequent acceleration and lane changes.

"We are the sinners," O'Dell said. "The driver has so much influence on the fuel efficiency of their car, but we want to blame the car."

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