2008 Geneva Motor Show: 2010 Mercedes-Benz S400 BlueHybrid

• Competes with: Lexus LS 600h L
• Looks like: A run-of-the-mill S-Class
• Drivetrain: 3.5-liter V-6 with electric motor and seven-speed automatic transmission
• Hits dealerships: Fall 2009

The Mercedes-Benz S400 BlueHybrid is a gasoline-electric hybrid version of the automaker’s flagship S-Class sedan that’s expected to arrive in the U.S. in fall 2009. Average fuel economy is about 30 mpg, according to Mercedes, which is nearly double the 16 mpg combined rating of the V-8-powered S550.

Though a gasoline-electric version of the S-Class is significant in its own right, the S400 BlueHybrid’s hybrid system also incorporates a lithium-ion battery pack. Mercedes says the operating temperature of the battery pack is regulated by the car’s air conditioning system, thereby enhancing battery life and performance.

Total system output of the 3.5-liter V-6 and electric motor is 299 hp and 277 pounds-feet of torque. Mercedes-Benz spokesman Rob Moran says the electric motor supplements the gas engine during acceleration. The automaker cites a zero-to-62-mph time of 7.3 seconds for the car and an electronically limited top speed of 155 mph.

Buyers of expensive luxury sedans haven’t had many eco-friendly alternatives to traditional V-8-powered models, and even the new Lexus LS 600h L is no fuel-saver with its 20/22 mpg city/highway rating. That’s about to change with the S400 BlueHybrid, which gives big spenders all the luxury they’d expect from an S-Class with significantly improved gas mileage.