Why Your Car's Mileage May Not Always Measure Up

By JOSEPH B. WHITE, WSJ

It's possible to get precise measurements of nearly every feature of a car, from trunk space to front hip room. But the most important attribute for many shoppers—fuel economy—is still just an estimate.

Drivers, regulators and car makers have long been vexed by the variance between the mileage figures published on a showroom vehicle's window sticker (which are based on Environmental Protection Agency testing protocols) and the car's real-world fuel consumption. Now, federal regulators and auto makers are rethinking how to close the gap between their fuel-economy estimates and actual mileage—particularly for vehicles that use newer technology, like electric-hybrid systems or turbochargers.

The 2013 Ford Fusion earned an EPA fuel-economy rating of 28 miles per gallon (combined city/highway). It didn't fare as well in Consumer Reports testing, which gauged its combined mpg at 25.

Consumer Reports, in a review of Ford Motor Co.'s 2013 Fusion sedan last week, questioned the fuel-economy benefits of Ford's EcoBoost engines, saying that in its tests, vehicles equipped with the turbocharged motors haven't delivered the promised fuel efficiency. The Fusion SE with a 1.6-liter EcoBoost engine achieved 25 miles per gallon overall in its testing, below the EPA's rating of 28 mpg and below Consumer Reports' results for other cars in its class, including the Honda Accord (30 mpg) and the Nissan Altima (31 mpg).

Ford says its own and third-party research indicates customers are satisfied with their EcoBoost vehicles.

(More here.)