Since mid-summer we've been keeping abreast of the latest round of three-cylinder rumors for Mercedes-Benz, and though there's still talk that the next generation of ultra-efficient fuel-sippers might sport only three combustion chambers, it's highly unlikely that will be the case--and even less likely that they'll be for U.S. consumption.

At first blush, the three-cylinder solution sounds good--smaller displacement, less mechanical components--it should mean cheaper to build and more fuel efficient engines, right? Thinking it through, however, it also means less low-end torque, more engineering resources, and the inherent difficulties in taming the vibrations and roughness of an unbalanced number of cylinders.

The Smart ForTwo already employs a three-cylinder engine, but it's a car not fit for the Mercedes-Benz brand in Europe or the U.S., despite being a Daimler family product. Without even a four-cylinder in Mercedes' current U.S. lineup, jumping immediately to a three-cylinder--with all the difficulties inherent in their very design--for the next-gen C-Class seems like an awfully long leap.

Especially when Mercedes already has so many other fuel-saving technologies in the works, including the DiesOtto engine prototype, its first set of hybrids in the form of the S400 and ML450, plus the efficiency yet to be extracted from the standard four-cylinder engine with the addition of technology like turbocharging and direct injection.

Though a three-cylinder engine is an interesting idea, it's just not ready for prime time in the luxury segment, at least here in the U.S., where we expect our cars to have power, style and efficiency--yes, we want it all, and we want it now.

In the mean time, you can check out what we know is in store for the 2011 Mercedes-Benz C-Class, including some leaked photos of the car.

[Autocar]

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