Auto shows have long been the industry’s fantasylands, places where automotive dreams come true. In other words, they’ve been geared to lavish displays of superpowered rides and futuristic concepts.

Yet while 600-horsepower sports cars like the 2009 Corvette ZR1 are still making their debuts at the North American International Auto Show in Detroit, more automakers are unveiling not the raciest, most powerful designs they can come up with, but fuel-sipping rides and alternative-fuel technologies. At this year’s show, which opens with media previews today, there is an unprecedented range of earth-friendly models. And that extends even to the luxury automakers, who have long pursued acceleration rather than conservation, but are showing off ethanol-eating S.U.V.’s, plush hybrid sedans, and more efficient diesel-powered sports coupes.  

Squeezing more miles from a gallon of gas is an especially delicate balancing act for makers of luxury cars, whose customers demand spacious, hefty vehicles with major muscle and all the latest gadgets. But automakers have seen the writing on the wall—or more accurately, on the mileage stickers affixed to every new car and truck: The 2007 energy bill signed into law in December calls for a nearly 40 percent jump in fuel economy standards over the next several years, the first major adjustment in decades, and eliminates mileage breaks for heavier S.U.V.’s, pickups, and minivans. (See slide show.)

“We can provide our models from Europe that tend to be smaller and have higher fuel economy,” said Thomas Plucinsky, BMW’s spokesman. “But U.S. customers still want larger vehicles, so the trick is to give them the size and performance they demand while still boosting efficiency.”

As a result, we have Detroit unveilings such as the Cadillac Escalade Hybrid, a gas-electric version of this three-ton monument to S.U.V. excess. On sale this summer, the electric-boosted Escalade is designed to deliver roughly 20 miles per gallon in the city, a significant gain over the 12 to 13 m.p.g. of the gas-only model.

G.M. developed its hybrid system with BMW and the former DaimlerChrysler, and both BMW and Daimler-owned Mercedes are showcasing their versions in Detroit. BMW’s X6 ActiveHybrid concept is a preview of a production crossover S.U.V. hybrid that will reach showrooms in 2009. (BMW claims a 20 to 25 percent overall gain in fuel economy.) Mercedes’ ML450 will incorporate the hybrid system when the midsize S.U.V. goes on sale the same year, along with a V-6 hybrid version of Mercedes’ flagship S-Class sedan.

David Cole, director of the Center for Automotive Research in Ann Arbor, Michigan, said that luxury buyers may be an easier sell for fuel-saving technologies—including hybrids and diesels—that still add thousands of dollars to the cost of a car. “Wealthier buyers can better afford to be green, and they probably pay more attention to how they appear in the eyes of the world,” Cole said. Diesels currently add roughly $1,000 to $5,000 to a model’s cost, while hybrid technology adds anywhere from $3,000 to $30,000, the latter for the Lexus LS 600h L sedan.