With the entire world moving toward greener everything, it follows that the upper crust would join in. After all, not everyone with a conscience wants to be seen driving a Toyota Prius.

That was the thought behind Eco-luxe, a swanky Manhattan event that gave journalists some prime schmoozing time with green marketers from every conceivable sector, from quintuple-filtered vodka made in low-landfill facilities to carcinogen-free water bottles. Eatery Rouge Tomate was brimming with worldly conversation, stiff cocktails and a few celebrity eco-product evangelists, such as Mariel Hemingway.

A few OEMs parked their alt-fuel vehicles prominently out front. Guests who wanted test drives held off on cocktails before sampling the rides, which Mercedes-Benz S-class product manager Bart Herring appreciated as he handed over the keys to the silky-smooth $87,000 eco-flagship, the S400 BlueHybrid, a mild hybrid that uses lithium-ion batteries to help it get ratings of 19/26 mpg city/highway. Did we mention that the S400 costs $3,650 less than the nonhybrid S550? That's a far cry from the nearly $5,000 premium Lexus charges for its hybrid RX400h.

“One day,” Herring said, “people will see mild-hybrid technology much the same way they do direct injection or turbo-charging. And in the mean-time, lithium-ion batteries will help to narrow the efficiency gap between full- and mild-hybrid vehicles.”

Audi officials say that a balanced mix of alternative-energy investments will win the day.

“The future requires a mix of tech, because consumers have not yet chosen one way over another,” said A3 product manager Carter Balkcom. “Battery range and EV infrastructure are not there yet, so diesel is the right technology for Audi. With the new A3 TDI, you get 42 mpg right now.”

The A3 TDI, which went on sale in September for $1,200 more than its gasoline counterpart, boasts the highest high-way mileage of any luxury passenger car. Balkcom also cited Audi's E-tron concept, which debuted at Frankfurt, as an example of the brand's continued interest in electricity.

As alternative powertrains become more mainstream in the minds of consumers, one wonders how long OEMs will be able to charge premium prices. Consumers will expect these technologies, no longer viewing them as alternative.

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(Pictured: The Mercedes-Benz S400 BlueHybrid combines a modified V6 gasoline engine with a compact hybrid module with lithium-ion batteries to give the luxury sedan fuel economy of 26 mpg on the highway; photo courtesy of Mercedes-Benz.)