Today we got some optimistic news from BMW on the future of diesels in the United States. In talking to journalists at the BMW University program at the company's U.S. headquarters in New Jersey, Tom Baloga, vice president of engineering for BMW of North America, expressed confidence that a four-cylinder diesel will show up in a range of U.S.-bound models during the next decade.

"You're going to see it of course in the 3 Series," he said, "and the 5 Series is a good possibility. If the performance [of such an engine] is sufficient in the X3, U.S. customers would likely accept it in the X5 as well."

Said diesel four-cylinder would be a 2.0-liter (as in the European 320d shown above), but BMW wouldn't be targeting the bargain end of the market.

"This engine needs to match the acoustic qualities of a 6-cylinder, and it needs to match the performance, as well as performing better in terms of fuel economy and emissions.

"Our four-cylinder diesel will be so good that people will readily accept it as a replacement for six-cylinders. The target is to produce enough horsepower to be comparable [in performance] to our N54/N55 six-cylinder turbos."