Consumer Reports finds small turbo engines don't deliver on fuel economy claims

Small turbocharged engines are marketed as delivering the power of a large engine, with the fuel economy of a smaller one. That's a tempting proposition, but our testing shows these small-displacement turbos are not delivering on the promises.

By now, we've tested many cars with these engines, and lots of competitors with traditional, naturally-aspirated powerplants, big and small. Generally, the turbocharged cars have slower acceleration and no better fuel economy than the models with bigger, conventional engines. Looking at EPA fuel-economy estimates (calculated based on laboratory tests), some of these cars' turbocharged engines seem to have an advantage. But we found those results don't match the findings from our own fuel-economy tests.

The latest example is the collection of EcoBoost Ford Fusions we tested, which come with small, direct-injection, turbocharged four-cylinder engines. The smallest one—a 1.6-liter producing 173 hp—is a $795 option over the basic conventional 2.5-liter four cylinder on Fusion SE models. But that car's 0-60 mph acceleration time trails most competitors, and its 25 mpg overall places it among the worst of the crop of recently-redesigned family sedans. The Toyota Camry, Honda Accord, and Nissan Altima, all with conventional 2.4- or 2.5-liter four-cylinder engines, get an additional 2, 5, and 6 mpg, respectively. And all accelerate more quickly.

The larger among Ford's EcoBoost four-cylinder engines, the turbocharged 231-hp, 2.0-liter, is billed as having the power of a V6 but delivering the fuel economy of a four-cylinder. However, our so-equipped Fusion Titanium returned 22 mpg (which pales against the 25 and 26 mpg we recorded for the best V6 family sedans), slower acceleration and reduced refinement compared to its V6-powered peers.

Another example is our tests of the Chevrolet Cruze. Our base Cruze had the 1.8-liter four-cylinder; our higher-end 1LT version came with the 1.4-liter turbo four cylinder. While the 1.4-liter feels marginally more powerful in daily driving, it was barely faster to 60 mph, and it got the same fuel economy as the larger engine—26 mpg overall.

Turbochargers pump extra air into the engine to deliver more power. But all engines have to be operated at a very specific air-to-fuel ratio. So this extra air has to be augmented with extra fuel, which may offset any savings from shrinking engine sizes.