Continuing to diversify the green powertrain options it offers to buyers, Mercedes-Benz will add a clean-diesel model to its largest sedan line, the S-Class.

The new 2011 Mercedes-Benz S350 BlueTEC sedan joins this year's S400 Hybrid, which adds a mild hybrid system with a 15-kilowatt electric motor to a 275-horsepower 3.0-liter V-6 gasoline engine (the only V-6 offered in an S-Class this year).

Dashboard - 2010 Mercedes-Benz S Class 4-door Sedan 5.5L V8 RWD

Dashboard - 2010 Mercedes-Benz S Class 4-door Sedan 5.5L V8 RWD

The new S350 BlueTEC model is the only diesel S-Class that will be offered in the U.S., and the first in roughly 15 years. Its 3.5-liter V-6 turbodiesel is the same one already sold in Bluetec versions of the ML, GL, and R-Class sport utilities.

Models for the U.S. will be fitted with the advanced version of the company's BlueTEC exhaust aftertreatment system, including the use of AdBlue urea injection. This is needed to meet U.S. emissions requirements, which are now the most stringent in the world.

This re-tuning means the U.S. S350 BlueTEC produces more power (241 horsepower) and torque (429 pound-feet) than the European S350 model (at 235 hp and 398 ft-lb). Power is delivered to all four wheels via the traditional Benz 4Matic all-wheel-drive system.

The S350 BlueTEC should equal or outdo the S400 Hybrid on fuel efficiency, but we'll wait for the EPA to render its decision. The hybrid S-Class is rated for 2010 at 19 mpg city, 26 mpg highway.

No word yet on pricing, but at $87,950, the S400 Hybrid is presently the least expensive model (and the only V-6) in the 2010 S-Class lineup. The 2011 S350 BlueTEC should come in at roughly the same level, or lower than any gasoline V-8 model in the big luxury sedan.

The 2011 Mercedes-Benz S350 BlueTEC will arrive at dealers early in 2011.