Hybrids, small turbos often fall short of EPA mileage estimates

People who care the most about getting great gas mileage may be disappointed to learn what Consumer Reports' latest tests have uncovered. It turns out that hybrids are all too often coming up short.

Hybrids tend to be very fuel-efficient. But many of those Consumer Reports tested got far fewer miles per gallon than their window stickers claim. For example, the Ford CMax hybrid. The Environmental Protection Agency says it gets 47 mpg overall. But in Consumer Reports' tests, it got 37 mpg—still good, but about 21 percent less than the EPA estimate.

Consumer Reports thinks the problem is that the EPA ratings are based on outdated tests that don't reflect real-world driving conditions for hybrids. Take highway driving, one of the tests the EPA performs on a dynamometer, which is essentially a giant treadmill. The EPA tests cars at simulated speeds averaging just 48 mph, with a lot of stop and go.

Hybrids do well in those driving conditions. They can often operate in electric mode without burning any gas. But Consumer Reports tests highway mileage on a highway, at a steady 65 mph, using a fuel meter to measure the amount of gas burned.

In those conditions, hybrids are constantly running their gas engine, so they burn more gas than they do in the EPA tests. Consumer Reports has discussed its findings with the EPA, and the agency says it's considering updating its tests.

Consumer Reports' fuel-economy tests also show that cars with small turbocharged engines often do not deliver on the mileage promised. Those include the Buick Encore, Ford Fusion, and Nissan Juke. They fell short of the EPA estimates by 10 percent or more.

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