Finally, MPG Numbers You Can Believe

We test the new fuel economy standards.

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"Your mileage may vary." For years, carmakers have put those words next to the gas-mileage figures they claim in ads and brochures, acknowledging an open industry secret: The numbers were bunk. Until this year, those mileage estimates, generated by the Environmental Protection Agency, had been based on tests developed in the 1970s—when engines were simpler and there were fewer onboard computers and other devices that drew power and lowered mileage. The advent of hybrids finally revealed how outdated the standards had become; the Toyota Prius, for example, received an EPA rating of 60 MPG in city driving, even though most users—including one of the EPA's own top officials—got real-world mileage in the 40s.

Mileposts

Real-world fuel economy vs. EPA estimates

Car New EPA
Estimate
Real World
Average
Percent
Above/Below
Volkswagen Touareg 14 18.1 29.3
Saturn Vue 18 17.2 -4.4
Cadillac STS 20 21.8 9.0
Subaru Impreza WRX 21 22.5 7.1
Audi A4 24 24 0.0

Source: EPA, U.S. News estimates

The EPA has retooled its mileage standards, starting with cars for the 2008 model year—and gotten it right, according to an informal U.S. News test. We calculated the mileage for five different test cars driven recently, with more than 200 miles logged in each. In three of those cars, the real-world mileage exceeded the EPA's new estimates, while one was about spot-on and one was slightly below. And we tend to favor sporty motoring, which means that drivers with a lighter foot might routinely beat the advertised numbers.

While '08 models are the first to be sold with the new estimates, the EPA's website, fueleconomy.gov, provides both old and new numbers for cars going back several years—allowing used-car shoppers to get more accurate information, too. In most cases, the new figures are about 10 percent lower, or a 2-to-3-MPG difference. For hybrids and other high-mileage vehicles, the difference can be 8 or 9 MPG. And that eye-popping 60 MPG for the Prius has been revised down to 48. Prius buyers might feel duped—but they can take heart from their role in forcing a rare government retraction.