2008 Paris Auto Show: 2010 Mercedes-Benz S400 BlueHybrid

• Super-low carbon emissions
• Fuel economy in the high 20 mpg range
• Still boasts almost 300 horsepower

• Not a full hybrid like Lexus LS 600h L
• Diesel S-Class just as thrifty, less complicated
• Less powerful than Lexus and BMW hybrids

BMW 7 Series Active Hybrid, Lexus LS 600h L

2010 Mercedes-Benz S400 BlueHybrid

It remains to be seen whether the market will respond to Mercedes' claim that the S400 BlueHybrid is the world's most economical luxury car when it arrives in 2009 (perhaps 2010 in America). Termed a mild hybrid, the 3.5-liter V-6 and electric motor -- powered by a lithium ion battery pack -- combine for 299 horsepower, while stop-start technology and brake regeneration contribute to the economical drivetrain. Mercedes says the S400 will cover the 0 to 60 in 7.3 seconds, but a light foot would be required to achieve the European cycle 30 mpg. Mercedes boss Dieter Zetsche said the S400 was only the beginning of a massive campaign to get greener, which will include an S300 BlueTec diesel hybrid in the near future.

Once upon a time, it was a safe bet that luxury car buyers didn't give a damn about the environment or gas prices, so the cars were often huge and guzzled gas without fear of consequences. Today, however, even the Republican presidential nominee thinks global climate change is human caused and now everything has to be green. Or, in the case of Mercedes, blue, as in BlueHybrid. This is the name Mercedes has given its mild hybrid technology, and it promises to give a fuel economy boost to those who want to drive green, but don't want a diesel.

From the outside, the Mercedes S400 BlueHybrid looks like every other S-Class on the road, with the exception of the exceptionally long "BlueHybrid" badge on the trunk. It's what's under the hood that counts here.

The gasoline-burning half of this gas/electric hybrid is Mercedes' 3.5-liter V-6. Boasting variable valve control and a few other tweaks, output is boosted to 279 hp with a reduction in fuel consumption. This combines with a 20-hp electric motor that generates an impressive 118 lb.-ft. of torque off the line, promising sprightly acceleration from a standstill and improving fuel economy as well. The engine also features standard tricks like a start-stop function when the car rolls to a stop. However, the electric motor is not able to move the car independently.

The idea of fuel efficient luxury cars used to be pie-in-the-sky, even with numerous diesel versions available in Europe. However, with the S400 BlueHybrid, Mercedes takes a step in the Lexus hybrid direction, arguably better, with a car that will offer the drivability Mercedes customers require, but with (theoretically) better fuel efficiency than the Lexus LS 600h L hybrid. Price will be the final determining factor, but if Benz keeps it reasonable – well, reasonable by luxury car standards – this could be a hit.

By Keith Buglewicz and Greg Brown Photo credit: Greg Brown