After a 10-year lapse, BMW may bring four-cylinder engines back to the U.S. to help it meet stricter fuel economy standards. The leading candidates would be the 1 Series and 3 Series compact sedans. BMW's plans may be an admission that no matter how much Europeans love fuel-sipping diesel engines, Americans are slow to catch on to the merits, or else have long memories of the horrible passenger-car diesels of the 1980s. BMW's current thinking comes via a Bloomberg report from Detroit.

The car that put BMW on the map in the U.S., the 2002 of Vietnam era, used four cylinders, as did the first 3 Series of the late 1970s, which enthusiasts considered woefully underpowered at 120hp. BMW threw in the towel on fours when it stopped bring the 318TI into the U.S. in 1999, but it's not clear if it was the four-cylinder engine or the hatchback configuration that did in the 318TI. Power won't be a problem: Many of the current four-cylinder BMW engines crank out 200hp. Tom Baloga, BMW VP of engineering for the U.S., told Bloomberg's Mike Ramsey, "The biggest challenge will be maintaining the 'Ultimate Driving Machine' performance." We think that's a given. The problem really is, "Can we get people to pay $35,000 for that car?" (Our words, not BMW's.)

About half of BMW's models worldwide have diesel engines: 1 Series, 3 Series, X3 compact SUV, and the entry level version of the midsize 5 Series sedan.  In the U.S., BMW offers a six-cylinder turbo-diesel engine on two models: the BMW 335d and the BMW X5 xDrive35. A four-cylinder BMW diesel that produces 204 hp was named Europe's engine of the year in 2008 but it's not offered here.

It was a four-cylinder engine in a 5 Series, by the way, that won a BMW vs. Toyota Prius fuel economy run. On a run from London to Geneva, half highway, half city, a much bigger BMW with a diesel engine actually used less fuel than a Prius.

Some of BMW's squeamishness was reflected in a late 2008 BusinessWeek article by David Kiley, "Is the U.S. Ready for Four-Cylinder BMWs?" According to Kiley, Audi's A4 isn't perceived as being in the same league as the BMW 3 Series and Mercedes-Benz C-Class  because 80% of the  A4's in the U.S. come with four-cylinder engines. It's possible younger buyers are less concerned by the number of cylinders. And to move four-cylinder cars into buyers' hands, BMW may tweak the pricing to make it advantageous to the buyer - as well as to BMW's corporate average fuel economy.