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Automakers are turning to smaller, turbo engines for better mpg

Consumer Reports News: July 24, 2012 08:38 AM

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In the past, four-cylinder engines have been mostly reserved for basic economy cars and lower-cost family sedans. More upscale, higher-priced vehicles usually came with a larger six-cylinder engine that wasn't as fuel efficient but delivered more power and refinement. But that's changing, as experienced in our latest compact SUV road tests.

To squeeze out better gas mileage, even luxury automakers have begun putting four-cylinder engines in their larger sedans and SUVs. By using turbochargers, they are able to build "four-bangers" that produce power similar to a larger engine, but with the fuel economy of a small engine.

Several SUVs fit into that group, including the recently tested Audi Q5 and BMW X3. Four-cylinder engines are now more refined, and modern turbos are more reliable and responsive, with much less "turbo lag" after you step on the throttle.

The four-cylinder engine in the front-wheel-drive Ford Edge, for example, is smoother than the V6, does not lack power, and gets 21 mpg overall, 3 mpg better than a V6 Edge with all-wheel drive. The Mercedes-Benz C250 sedan we tested last month uses a 1.8-liter turbo four that is the smoothest four-cylinder engine we've ever tested.

On the other hand, the four-cylinder X3 and Q5 aren't quite as smooth as they were with six-cylinder engines. They can sound a little buzzy, and the direct injection they use causes them to emit a muted diesel-like clatter at idle.

With the push for better fuel economy, we'll probably see more of that trend.

See our fuel economy guide for tips on saving fuel with your current vehicle.

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