Are Government Fuel Efficiency Numbers Pumped Up?

A new Jeep Liberty Diesel gets 22 mpg in city driving, according to Environmental Protection Agency tests. That sounds like great news for drivers tired of high gas prices. But is it true?

"In the city we actually got 11 miles per gallon," said David Champion, who heads up Consumer Reports' auto testing facility.

Cars Fall Far Short of EPA Mileage Estimates in Test

With prices at the pump soaring, many new car buyers are looking more closely at fuel efficiency ratings.

Those stickers placed on new car windows tell buyers how many miles per gallon they can expect to get driving on stop-and-go city streets and on highways.

But when Consumer Reports tested more than 300 cars for an investigation on fuel economy, what it learned may shock you.

Champion said its mileage estimates were much lower than the EPA's — in some cases, half as much.

That means drivers of the Jeep Liberty Diesel may end up spending twice as much on fuel than they might have expected.

Consumer Reports tested the cars in rural Connecticut, on a course that imitates real-life city driving. They also tested for highway driving and a mixed-driving trip. Then they measured fuel levels. Champion said his testers found a shortfall in the miles per gallon listed on the official stickers in about 90 percent of the 300 cars they tested.

Hybrids Get Good Mileage, But Less Than Advertised

Champion said his group found the biggest shortfalls in fuel-efficiency ratings among hybrid vehicles. "We found large discrepancies between what we got in the city cycle and what the EPA said they got," he said.

Consumer Reports tested the Ford Escape hybrid and found it averaged 26 miles per gallon on a trip that mixed city and highway driving. The EPA estimates that the front-wheel-drive Escape gets 36 mpg in city driving and 31 mpg on the highway, according to Ford's Web site. The site notes that your actual mileage will vary based on driving habits. The Honda Civic sedan hybrid came up 46 percent short of the EPA mileage rating.

Champion does stress many hybrids are extremely fuel efficient — even though they fell short of the EPA estimates during Consumer Reports' tests.

The Toyota Prius, a hybrid, got an average 44 miles per gallon in the Consumer Reports tests. The EPA said the vehicle averaged 60 mpg in the city and 51 mpg on the highway.

While a car averaging 44 mpg may save you money at the pump, it will still cost you more to get it off the showroom floor.

"If you're just looking at buying a hybrid for financial gain, then they don't really make sense. It's going to take you five to 10 years to pay back the increase in cost. If you're looking at it from an environmental point of view, you are saving gas, and they are extremely clean in terms of emissions," he said.

Consumer Reports found other fuel efficient cars that are not hybrids: the Toyota Corolla and the Honda Civic.

Group Blames Outdated Tests

Champion said the EPA numbers aren't meaningful because the agency's test is out of sync with today's driving habits. "I think their test is basically outdated. It's based on the 1970's type of driving style," he said.

The EPA gets its mileage numbers through laboratory tests. They measure emissions instead of fuel, and the test has remained unchanged for 20 years.

Today, we spend more time driving in city and suburban settings, where traffic is stop-and-go; we also drive faster on highways.

The EPA acknowledges that its mileage ratings system needs an overhaul. "We recognize that the test that is done today is not accurate, and we want to do a better job to fix it," said Margo Oge, head of transportation and air quality at the EPA.

Oge says one reason to change the test is to improve on the statistic that only 50 percent of drivers get the mileage the EPA posts.

"We're going to try to change that. We're gonna try to come up with a number that will basically [match] 75 percent of the people, not 50 percent," she said.

Oge agrees that the discrepancy between the EPA numbers and the Consumer Reports test should be addressed, but stresses that the government fuel-efficiency ratings are estimates. "We're working very hard to change the numbers. But if you look at this label, the label basically says, 'Estimated number.' … There is no such thing as a perfect test that can reflect, accurately, how you drive versus how I drive," she said.

By the end of this year, Oge says, there will be a proposed new test. But it will take two years before the test is put into action. Meanwhile, those "Estimated Miles" will remain on new car stickers.

Champion believes that is too long a wait. "It's a disservice to the American public. ... I think they are getting incorrect information to make a purchasing decision," he said.

He also says car manufacturers are partly to blame.

"It's the way that the manufacturers are using those mileage numbers -- for advertising -- which inclines them to make them more optimistic than they would normally," he said.

Car companies told "20/20" they are required by law to post those stickers and they are working with the EPA to improve the testing.

Fuel-Saving Tips

In the meantime, there are things you can do to conserve gas:

  First, slow down on the highways, and use cruise control.

  Link your errands together so you take advantage of a warm engine, rather than starting cold every few hours.

  Consumer Reports also suggests keeping the pressure on the gas pedal steady when you drive. Bear down gently and don't floor it when you accelerate.

  Coast to a stop; don't slam on the brakes.

  When you're waiting, turn the car off. Idling wastes gas.

  Regularly check your tire pressure. Improperly inflated tires are unsafe and waste fuel.

As for using the air conditioner, go ahead. It has little impact on gas mileage.

"Really, if you're looking to buy a fuel-efficient car, don't buy too much car," Champion says. Heavier cars use more gas. Remove luggage and bike racks when you're not using them. They add weight and decrease the aerodynamics of the car.