Vanilla Option.(Special Report)(eco-friendly cars)(Cover story)

Byline: Barrett Sheridan

The next revolution in green cars is more likely to come from ordinary combustion engines than some exotic technology.

The Fisker Karma has a sleek, luxurious look that seems to scream "future!" A sedan created by a former designer for BMW and Aston Martin, the Karma is a plug-in hybrid, much in vogue in these days of enthusiasm for all things green. After charging overnight from an ordinary wall socket, the Karma can run on electricity for up to 80 kilometers before a gasoline engine kicks in. The car, slated for production next year, probably turned more heads at the recent Detroit auto show than any other concept car. But good-looking as it may be, the Karma isn't likely to populate the streets in significant numbers any time soon. Like many of the hottest new green-car designs, it carries a high retail price tag--a cool $80,000.

The green auto revolution of the next 10 to 20 years may revolve around a far more mundane technology: the conventional combustion engine. After 120 years of engineering, it's hard to believe that engineers can wring any more efficiency out of the humble car engine, but they can. Partly because consumers of the last few decades put a greater a premium on power than fuel efficiency, there are a thousand and one incremental improvements--some of which have already reached the market--that can potentially turn the average sedan into a machine even Al Gore could love. Taken together, they can easily--and cheaply--boost fuel efficiency by 20 percent or more in the next decade. That's a faster and cheaper improvement than any green technology is likely to yield. "The internal combustion engine is fighting off the competition by improving," says Michael Omotoso, a forecaster with J.D. Power and Associates. "We don't really see it going away any time in the next 20 to 25 years."

The pressure to put greater numbers of gas sippers on the highway largely comes from consumers now balking at triple-digit oil prices and concerned about our toaster-oven globe. The European Union has proposed new legislation that would strictly limit auto emissions on the Continent, and already several European countries, notably France, are experimenting with tax rules that penalize carbon-spewing behemoths and reward compacts. Even the United States is now tightening fuel-efficiency standards.

The green tide of opinion has already lit a fire under engine designers, who are readying new technologies. For instance, gasoline direct injection, or GDI, delivers fuel more precisely by injecting it directly into the combustion chamber, rather than an intake manifold. (The technology has existed for years, but only now is being included in mainstream vehicles.) That provides an efficiency boost of up to 10 percent, according to an analysis done last month by the PricewaterhouseCoopers Automotive ...