Thanks to more stringent CAFE regulations just over the horizon, BMW will once again offer a four-cylinder engine in the U.S. market. Rumors of a four-pot BMW first surfaced earlier this year, but a BMW engineer has confirmed the more fuel-efficient engine is U.S.-bound.

BMW hasn’t offered a four-cylinder model in the United States since 1999, but the German automaker will bring back the smaller engine as it brings its lineup up to spec with looming emission regulations.

However, the move to four-cylinders won’t be easy as a simple engine swap. BMW has built a reputation for producing performance vehicles, and the automaker doesn’t want to erase that in the name of better mileage. “The biggest challenge will be maintaining the ‘Ultimate Driving Machine’ performance,” Tom Baloga, BMW’s vice president of engineering for the U.S., told Bloomberg.

Although about 50 percent of BMW’s global sales are made up of four-cylinder vehicles, Americans have come to associate BMW’s with powerful models. However, BMW will have to find a way to balance performance and fuel economy as it raises its fleet wide average from 26.5 mpg to 35.5 mpg by 2016.

Diesels promise to also factory heavily into BMW’s CAFE plans, including four-cylinder oil burners. BMW’s most fuel efficient model – the 116d – uses a four-cylinder diesel capable of returning better than 53 mpg. In fact, Baloga says BMW’s European offering could meet the 2016 CAFE regulations, thanks to a 67 percent take rate on diesel engines.

Despite the confirmation, Baloga failed to mention which BMW models are earmarked for a four-cylinder. However, the 1- and 3-Series seem like a safe bet, with an entry-level 5-Series model not completely out of the question.