Milling over a car engine
Milling over a car engine - 
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Tess Vigeland: A new version of the ultimate driving machine will make its debut on dealer lots across the country this fall. BMW says the sedan will have all the performance and styling you'd expect of a top luxury vehicle. But the engine? 4-cylinders -- something that hasn't been seen on a BMW in this country for more than a decade. And BMW's not the only one paring down.

As Marketplace's Alisa Roth tells us, a combination of consumer demand and government standards are driving the changes.

Alisa Roth: Twelve years ago, BMW stopped selling cars with 4-cylinder engines in the U.S., because the company felt that to be seen as a true premium brand here, its vehicles needed at least 6-cylinders.

But times have changed. American drivers -- and the American government -- are demanding better fuel efficiency.

Tom Kowaleski is a spokesman for BMW North America. He says new technology has changed the relationship between cylinders and performance.

Tom Kowaleski: We gain more performance than we had with the corresponding 6-cylinder engine that it replaces, but we do so with a 20 percent increase in fuel efficiency.

That's partly because smaller engines weigh less, so suspensions can be lighter too, and lighter cars are more fuel-efficient.

More and more carmakers have been coming to the same conclusion; one of Ford's best-selling full-size pickups now runs on 6-cylinders instead of 8; and Hyundai has stopped offering a V-6 version of the Sonata.

Michael Robinet is a consultant at IHS Automotive. He says keep in mind, these are global vehicles.

Michael Robinet: And so offering a 6-cylinder just for the United States doesn't make a lot of sense when you can offer a 4-cylinder in all markets.

BMW says it will keep making those bigger engines. But it does plan to start offering 4-cylinder engines in many more models.

I'm Alisa Roth for Marketplace.