Tighter emissions standards and fuel economy demands means we know BMW and Mercedes will return to four-cylinder engines in the U.S.; it's just a question of how many versions will they bring? BMW North America's CEO Jim O'Donnell said, "The plans will be firmed up when we have definite news from Washington on what the fuel standards are going to be."

BMW is no stranger to four-cylinder engines. It's the four-cylinder engine that helped BMW get into modern car production. In fact, its headquarters in Munich, Germany was built in the shape of four cylinders as a tribute. So it's almost ironic that BMW has not sold a car with a four-cylinder engine in the U.S. (one of its largest markets) for over a decade.

The first Bimmers in North America with the smaller engines should be the 1 and 3-Series lines, including the X1 and X3 SUVs. These smaller engines will likely also include turbochargers.

The return for Mercedes won't be quite as dramatic. It only stopped selling turbo fours in the U.S.-bound C-Class cars in 2005. It will likely return the gas-powered turbocharged four-cylinder engine to the C-Class->ke1593 and add it to the GLK->ke2078.

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