Germany's strongest premium brands in the U.S. sell cars at home that wouldn't fit their image abroad, including tiny city cars and any number of diesels. Nevertheless, the rise of fuel efficiency as a primary buying criterion has reportedly driven the company to consider introducing a four-cylinder 3-series to North America.

The move would almost certainly boost sales, since the European 320i, powered by a 167hp (124kW) petrol four-cylinder is already one of the company's strongest-selling models. The same powertrain in the 120i also collects good sales results, and would make sense, though at present only the 3-series is being considered for U.S. sale, reports Edmunds. Rival Mercedes has already decided to bring four-cylinder cars, including its new diesels, to the U.S. and Canada in 2010, proving even luxury and premium brands aren't entirely immune from the more mundane considerations of efficiency.

BMW won't be bringing its small diesels to the U.S. any time soon, however, content to rely on its four-cylinder petrol engines for now. Rising CAFE standards may push even that decision forward, as their efficiency is undeniable, though so too is the difficulty in certifying particulate emissions to meet the standards of all 50 U.S. states. The company also doubts its typical American buyer is truly ready to contemplate the idea of an oil-burner lying under the hood of his or her luxury-performance sedan.