Surprisingly, Detroit this January is greener than it has been in decades. Almost every new vehicle introduction at the North American International Auto Show (NAIAS) featured a high-mileage, hybrid, or clean-diesel car. Those vehicles that weren't introduced with a greener-than-thou proclamation included gasoline-saving technologies, such as the Ford "EcoBoost" powertrain that combines direct-injection and turbocharging.

All this comes less than a month after Congress required automakers to increase fuel economy by 40 percent by 2020, amid industry protests that such gains weren't feasible.

At the show, automakers embraced diesel engines because they can save as much as 30 percent in fuel economy and greenhouse gas emissions compared with gasoline engines. And the latest diesels are powerful, quiet, and nearly as clean as gas engines. Pollution control technologies have flourished since cleaner, low-sulfur diesel fuel was mandated in the end of 2006. This year most German manufacturers were touting new urea injection systems that will further reduce pollution.
For example:

• Audi rolled out a V12-diesel-powered version of its exotic R8 supercar with 500 horsepower that the company says gets 28 mpg.
• BMW had two diesels, a 3 Series sedan and an X5 SUV. Both have twin-turbocharged engines that make 265 horsepower and use urea injection.
• A small Mercedes-Benz SUV concept, called the Vision GLK Freeside, uses a 170-hp four-cylinder diesel.
• Cadillac showed a coupe version of its CTS sports sedan that design director Ed Welburn said "could" have diesel power.
• Like Cadillac, the Land Rover LRX concept was conceived as having a diesel engine should it move to production, with officials stating that a diesel was being developed for other models.
• Dodge, Ford, and Toyota each announced that they would put new diesel engines into their light-duty pickup trucks, though not until 2010.

In addition to diesels, the auto show was full of futuristic plug-in hybrid-electric vehicles. Plug-in cars get their main power from a regular electrical outlet, but they also have an auxiliary gas or diesel engine to charge the battery for longer trips. The biggest benefit is that if the batteries can provide 40 miles of driving, 78 percent of Americans could handle their normal everyday drives on just electricity. While conversion companies have been modifying the current Prius to plug in for some time, it will be at least until 2010 before factory plug-in hybrids advance from just demonstration vehicles to mainstream production.

Among those models at the show that we're told are headed for production are:

• The Fisker Karma—an exotic luxury sports sedan designed by Henrik Fisker, who previously penned Aston Martins and the BMW Z8. It will use the largest hybrid battery pack in any current car, giving it a range of 50 miles on just electricity, according to Fisker. For longer trips, the car will have a 2.0-liter gasoline engine driving an on-board generator to charge the batteries. Fisker claims the $80,000 car will go on sale at the end of 2009, which would likely make it both the world's first production plug-in, and the world's first production series hybrid (one with no mechanical connection between the gas engine and the wheels).
• The Saturn Vue plug-in hybrid, which GM says will have a 10-mile electric-only range, will go on sale in 2010.
• The Toyota Prius plug-in, which is just a current Prius converted by Toyota. It has a second nickel-metal-hydride battery pack that is reported to give it an electric range of about six miles. Toyota calls it a "blended hybrid," meaning the gas engine starts whenever it is beneficial. (It always runs above 35 mph.) The car is meant just to draw attention to the fact that Toyota says the next-generation Prius will be a plug-in.

Other plug-in hybrids in Detroit this year included:

• A Ford Escape demonstration vehicle with a 30-mile electric range that is being used by an electric utility company in Southern California.
• The Volvo ReCharge concept, a plug-in version of a Volvo C30 coupe with electric motors in the wheels previously shown in Los Angeles. The ReCharge is an all-wheel-drive series hybrid that is powered by four electric motors, one in each wheel. A 1.6-liter gasoline engine powers a generator to charge the batteries for extra range. Volvo claims a battery-only range of 62 miles.
• The Saturn Flextreme, a midsized car-based SUV concept that uses GM's E-Flex hybrid architecture. General Motors says the diesel-electric-powered Flextreme could go 34 miles on an electric charge.

Getting affordable batteries strong enough for plug-ins depends on developing lithium-ion technology, which saves weight and packs more power into a smaller package. So far, no lithium-ion batteries suitable for cars are commercially available, according to automakers. But Toyota jumped ahead in the race to develop plug-in hybrids by announcing that it would begin building its own batteries (with partner Panasonic) by 2010.

James Holland, Ford's chief engineer for the plug-in Escape, says the company is looking for a new business model to support plug-in hybrids. Possible scenarios could include leasing batteries to consumers, or selling the batteries separately from cars, and reselling them to electric utilities when it's time to trade the car in.

Diesels and plug-in hybrids weren't the only fuel savers at the show. General Motors and Chrysler each showed new fuel-cell concept vehicles, and Dodge rolled out the all-electric Zeo sports car concept.

Mazda showed the hydrogen-rotary-powered Mazda5 Hydrogen RE Hybrid. Its rotary engine can run on either hydrogen or gasoline, and a hybrid system boosts fuel economy on either fuel. The third-row seat is removed to make room for the large hydrogen tank.

Ford announced a new line of smaller, more powerful gasoline engines called EcoBoost that will replace larger, thirstier ones in some popular vehicles. EcoBoost engines will use turbocharging and direct fuel-injection technology to deliver increased power from smaller, more efficient engines.

General Motors rolled out two ethanol-powered concepts, the Hummer HX and Saab 9-4X. GM President Richard Wagoner says biofuels such as ethanol are needed in the short term to bridge the gap until technologies such as plug-in electric cars and fuel cells are ready for production.

While Toyota is investing in batteries for plug-in hybrids, GM announced it is joining a co-operative venture to develop ethanol made from non-corn feed stocks. GM and partner Coskata say their new process can make ethanol from everything from wood chips to used tires, and do so relatively inexpensively.

The sheer number of these gas-saving cars in Detroit dwarfed the rollout of two redesigned full-sized pickups and one ground-pounding 620-horsepower Chevrolet Corvette ZR1. Even many of "regular" cars at this show represent reasonable-sized and more efficient alternatives to large SUVs.

General Motors Vice President of North American Operations Troy Clark summed up the show well when he said: "We've always said new fuel economy regulations would have to be met with technology, not with smaller vehicles. That's what we're seeing here."

—Eric Evarts

See our complete coverage of the 2008 Detroit auto show. And discuss the event in our auto show forum.