Why that fuel sipper is a pocketbook sapper

The average car on America's roads could be 30 percent more fuel efficient using today's technology. Instead of getting 27.5 miles per gallon of gasoline, it could hit 40 m.p.g.

There's just one hitch. The technology is pricey.

So instead of bolting it into today's mid-priced models, automakers are planning to install the technology on luxury cars, where profit margins are higher. Eventually, those high-tech advances will find their way into the family sedan, experts say. And some of them, such as Mike Allen, who covers cars and new technology for Popular Mechanics magazine, expect the move will happen within five years.

"The threat of higher [federal fuel efficiency] standards is no longer driving this," he says. "The marketplace is."

But automakers counter that bundling several high-tech systems into mainstream cars would push prices out of reach for many consumers.

Indeed, in a 2004 J.D. Power survey, only 19 percent of new car buyers said they would consider buying a hybrid-powered vehicle if it cost $4,000 more than a comparable traditional car - the figure the company estimates it costs automakers to add the feature. The study also cites a "rebound effect." Essentially that means "for every mile- per-gallon increase in fuel efficiency, Americans just end up driving more miles," says Walter McManus, an analyst with J.D. Power and Associates in Troy, Mich.

The technology itself is hardly exotic. In a 2001 report, the National Academy of Sciences listed several types of technologies available today that could improve fuel economy, including hybrid drivetrains, more efficient engines and transmissions, lightweight materials, and improved aerodynamics.

As automakers adopt these, they are plugging them into high-end models with large profit margins. The most promising examples come from Lexus and Honda.

In January, Lexus debuted its 400H hybrid version of the all-wheel-drive RX330 sport utility vehicle. The 400H will offer 40 more horsepower than the RX330 and a continuously variable transmission.

Honda announced it will add hybrid electric power to a premium version of its mid-size Accord sedan. Along with an electric motor and a small battery pack, the new Accord also offers cylinder cutout technology. The system saves fuel by shutting down three of the engine's six cylinders when they're not needed to accelerate. Like most hybrid systems, Honda's "integrated motor assist" shuts the gasoline engine down when the vehicle is stopped, so it doesn't waste fuel idling. The engine springs to life as soon as the driver steps on the gas. Expect the new hybrid Accord to cost $4,000 to $5,000 more than today's top-of-the-line Accord V6.

Hybrid drivetrains, cylinder cutout, and "idle-stop" features were three of the engine technologies listed in the NAS report. Two others were wider adoption of variable valve timing - used in many Japanese engines and some sports cars today - and common-rail direct fuel injection, used mainly overseas because of emissions tradeoffs.

Other automakers rolling out such features include Ford, with its 2005 Escape hybrid SUV, Mercedes-Benz in two new hybrids, and Toyota, which hinted at using hybrid power in its upcoming FTX pickup. Subaru showed off a new advanced hybrid powertrain in its B9SC concept car, which may never see the light of day, but whose engine probably will. Mitsubishi showed a hybrid-powered Eclipse sports coupe.

General Motors and Chrysler each promised big V8 engines that shut down four cylinders under light throttle. GM will include the technology, "displacement on demand," on its most popular V8 engine in its truck lineup, including big pickups, SUVs, and vans. And Chrysler will use the technology on the high-performance V8 in its new line of big cars. Both will sell in large volume - and make at least a small dent in national fuel consumption.

Volkswagen, meanwhile, is committed to diesel engines, the most inherently efficient internal combustion technology. It has showed a small two-seat diesel that gets more than 100 m.p.g., and will introduce a Touareg SUV next year with a 365-horsepower turbodiesel that gets better mileage than the sport utility's regular V8.

Several automakers also introduced more efficient automatic transmissions as outlined in the NAS report.

Already BMW, Mercedes-Benz, and Audi offer cars with six-speed automatic transmissions. Audi, Honda, Nissan, Saturn, and Toyota offer continuously variable transmissions, which keep the engine operating at its most efficient speed. And Audi offers a new technology - a twin-clutch manual transmission - in its TT sports car, which does away with the power-sapping and fuel-robbing tradeoffs of traditional automatic transmissions.

Meanwhile, Ford is working on a new transmission for big pickups that uses hydraulics to mimic the effect of a hybrid's electric motor. When the driver demands little power, extra power from the engine is diverted to a hydraulic cylinder. When more power is needed, the cylinder pumps it back into the transmission.

Greater use of lightweight materials, however, is progressing more slowly. While Audi has proven the viability of producing a large all-aluminum sedan, only Jaguar, Range Rover, and a few low-volume sports-car makers have followed the lead, and only with expensive cars selling for $75,000 or more. Advanced plastics are finding their way into interior and engine components. But safety and liability concerns are limiting their adoption in body construction. And they're expensive.

While hydrogen fuel-cell powered cars remain the holy grail to reduce the nation's dependence on oil, they remain at least 10 years in the future. Experts believe a combination of current technologies will fill the gap.