In the world of cars, “sexy” and “socially responsible” have rarely fit in the same garage.

Henrik Fisker wants to change that. The former and Aston Martin designer sees his sedan as the new face of luxury: a plug-in hybrid with movie-star looks, sports car performance and a 100 mpg conscience.

And Fisker isn’t alone. From Mercedes to to Cadillac, the world’s luxury automakers are riding the green bandwagon. Skeptics may see that as a response to fuel economy and greenhouse-gas standards that could spell trouble for things like V12 engines and massive horsepower — traditional bragging rights for posh automakers. But whether the car companies are driven by pure hearts or pure business necessity, the results would be the same: a new breed of luxury or sports car that makes high mileage and reduced emissions key selling points.

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The idea of wrapping good citizenship in fragrant leather is not new. has built its image in part with hybrid versions of its popular sedans and SUVs. At the Detroit Auto Show in January, the luxury division revealed the Lexus HS 250h sedan. The first dedicated luxury hybrid — there will be no gas-only version — goes on sale this summer, promising roughly 33 mpg.

What’s different is that virtually every luxury automaker wants a piece of the fuel-saving action. Their crystal balls have gone cloudy, and no one wants to be out of the picture when the mists part.

“Every automaker faces an incredibly uncertain future in fuel economy, in regulation, in market demand,” says analyst Jim Hossack of AutoPacific. “If you’re not looking at every available technology, you risk getting caught off base.”

Unsure of what to order, companies are grazing from every corner of the tech menu. As I’m writing this, I’ve been testing clean-diesel versions of the BMW 3-Series sedan and X5 sport utility. The 335d posted a knockout 37 mpg on the highway, yet is every bit the sports sedan that BMW fanatics expect. Mercedes, and VW have also rolled out high-mileage 2009 diesel models that produce about 20 percent less carbon dioxide than comparable gas models, and are clean enough to meet even California’s strict emissions standards.

But there’s more than the usual diesel suspects. Mercedes will offer the S400 BlueHybrid this fall, a mild hybrid version of its flagship S-Class luxury sedan. Mercedes claims the S400 will deliver roughly 30 mpg with its gasoline V6 and small electric motor. Mercedes will also market a full hybrid version of its ML-Class sport ute, using the “two mode” hybrid system developed by General Motors, BMW and the former DaimlerChrysler.

BMW will fire back with hybrid versions of its X5 and X6 sport utilities. Porsche will offer a V6 hybrid version of its Cayenne S sport utility in 2010, followed by a hybrid offshoot of its new Panamera sports sedan.

Discuss: 
What do you think about the greening of the luxury market? Is it a publicity stunt, or have the elite grown a conscience?

On the concept front, BMW has showed a hybrid version of its full-size 7-Series sedan. The 7-Series ActiveHybrid uses a compact electric motor to add 20 horsepower to the company’s 450-horsepower twin-turbo V8, while trimming fuel consumption and emissions by 15 percent. showed the Converj, a striking plug-in hybrid, at the Detroit Auto Show.

Fisker’s Karma is scheduled for sale this fall at an almost suspiciously affordable $87,900 — about the price of a conventional full-size luxury sedan. For that price, buyers would get a lithium-ion plug-in that covers 50 miles on battery power alone, with a GM-based 4-cylinder engine boosting the driving range to 300 miles. But the Fisker looks more like an Italian exotic than a traditional luxury car. And it bakes in one-of-a-kind features such as a solar roof panel that generates enough juice for an extra five miles a week of driving range.