Four-cylinders overtake sixes as America's most popular engine

For the first time in modern history, the four-cylinder engine has become the most popular choice in the United States.

More American new car buyers are taking home vehicles powered by just four-cylinders than ever before, although that doesn't necessarily mean that drivers are satisfied with less power.

According to research by IHS Automotive, 43 percent of all new cars delivered in the United States during the first six months of 2011 were motivated by four-cylinder power, a reversal from 2005 when a similar 43 percent were powered by sixes. The remaining 57 percent of cars sold in the first six months of this year featured six, eight or twelve-cylinder propulsion.

Take fleet sales, which include an especially large number of V8s in trucks and vans, out of the picture and more than half of all new retail sales in the first six months were four-cylinder-powered vehicles.

That's a huge contrast from just a few years ago, when gas was less expensive and four-cylinders were generally relegated to low-buck econoboxes. In 2005, one in every three new cars featured a V8; by early 2011, that figure fell to just one out of every six vehicles.

While buyers undoubtedly have fuel economy on their minds more today than they did a few years ago, they're getting more engine for their money than ever before thanks to massive technological leaps.

A 2.0-liter four-cylinder in a compact Ford Contour in 1999 was rated at just 120 horsepower and it achieved EPA mileage estimates of 19/28 mpg (when converted to the EPA's current measuring scale). By contrast, a 2011 Ford Focus is rated at 160 horsepower from a similarly-sized four-cylinder (albeit one with variable cam timing and direct injection) and it is capable of netting as high as 40 mpg on the highway when optioned up with a special efficiency-oriented package.

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