mid the vast bazaar of the World Congress of the Society of Automotive Engineers, the booth for the American Foundry Society's honorees is hundreds of yards from the glamorous concept cars. Here, laid plainly on a table, is a dull gray sweep of metal -- the back side of an instrument panel for a Cadillac DeVille. From the size of it one would expect it to have the heft of a large suitcase, but instead it's as light as an aluminum lawn chair. Actually, it's made of magnesium, which is at least five times more expensive than steel but, for this part, is 70 percent lighter. Magnesium can be cast directly into complex three-dimensional shapes, minimizing costly finishing labor, and it requires less time to design both the part and the tools for making it. The final piece, therefore, is ultimately cheaper than its steel counterpart, as well as lighter, stronger, and more versatile. On the next table is a steering knuckle -- an obscure but significant link between the steering wheel and the wheels on the road. It's been forged from aluminum and is 40 percent lighter than the iron it replaces.

This drive to simplify assembly and remove mass is constant in the industry, spurred by relentless competition on price. Because mass is the enemy of fuel economy, these undercover improvements could lead to increased efficiency -- right now -- but instead they are going into larger, heavier, and more powerful vehicles. The net result: Innovation subsidizes waste.

There is even more potential under the hood. An array of engine improvements fly under the cover of jaw-breaking names such as "multi-valve, overhead camshaft valve trains," "variable valve timing," "intake valve throttling," and "camless valve actuation." Other concepts are more scrutable. Cylinder deactivation turns off parts of an engine when they're not needed. Smaller engines can be supercharged or turbocharged to provide punch for passing. Automatic transmissions can be made more efficient, and so can various accessories. Air-conditioning and power steering are essentially engine parasites, so the more efficient these are, the better the mileage. Even improving lubricants and tires can boost fuel economy.

A National Academy of Sciences panel estimated in 2001 that by using available technologies such as these in combination on a small SUV, it could cost as little as $465 for automakers to raise overall fuel economy 10 percent, $1,543 to raise it 30 percent, and $2,580 to raise it 50 percent. By comparison, Ford's new Hybrid Escape -- utilizing what is, for the foreseeable future anyway, the more expensive technology of hybrid engines -- costs $3,300 over and above the comparable V6 Escape. While the hybrid's city mileage is 50 percent better than the non-hybrid model, the highway mileage benefit is less than 20 percent. The National Academy panel, which was established by congressional mandate, came under intense political scrutiny when a draft of its report was leaked to the industry in early summer of 2001. After the report's official release, G.M. and DaimlerChrysler demanded -- and received -- a private audience with the panel to raise objections. In October 2001 the panel reconvened for further consideration. Though its members concluded that more stringent fuel economy standards benefited both consumers and the national interest, they chose not to recommend a raising of standards in their final report: "Given the choice, consumers might well spend their money on other vehicle amenities, such as greater acceleration or towing capacity, rather than on the fuel economy cost-efficient technology packages."

"Consumer choice" -- this is Detroit's code for "no new regulations." Why should it stick its neck out to build fuel-efficient cars that consumers, crazy over horsepower and size, will not buy? A new car model represents a billion-dollar investment. Everything from the scent of Cadillac leather to a pickup's throaty rumble is strategically engineered, focus-grouped, tweaked, and then marketed for maximum emotional impact. Cars often compete on trivial details. Missing a trend as simple as retractable cup holders can cost millions.

To get a glimpse into the marketing psyche of the auto industry, you could talk to medical anthropologist Clothaire Rapaille, a consultant to the auto industry who posits that a "reptilian brain" governs our automobile purchases. "The reptilian brain functions in the now time," Rapaille explains. "I'm going to go to the supermarket. And I'm afraid that somebody is going to attack me right now. So I'm going to take a Hummer to go shopping." Rapaille was enormously influential in articulating this fear-based marketing rationale for the SUV in the 1990s. Preying on our most ancient fears helped create an apparently unquenchable market for light trucks (SUVs, pickups, and minivans); in just two decades the American market moved from 20 percent light trucks to more than 50 percent, helping drive the fuel economy of our nation's cars to its lowest point since the 1980s.

This downward trend has been subsidized by the notorious "SUV loophole" in the government's Corporate Average Fuel Economy (CAFE) standards, national guidelines for fuel efficiency. Originally enacted after the energy crisis of the 1970s, the law exempted light trucks -- then a small share of the market and primarily used as work vehicles -- from the more stringent fuel economy standards for passenger cars. Indeed, CAFE standards have not been significantly raised in more than two decades, thanks to our elected representatives in Congress and their financial patrons in the car industry (including car dealers), who pump millions of dollars into campaign coffers -- $4 million in 2002 alone, when the Senate last defeated a proposed increase in CAFE standards. (Since 1990 the industry has given more than $97 million to congressional and presidential campaigns, 75 percent of that to Republicans. See "Priming the Pump.")

While U.S. carmakers and lawmakers fought for the status quo, Honda upped the fuel economy of its Civic by 5 to 10 percent in 2001 and debuted its hybrid Insight. That same year, Ford devoted much of its energy to doing damage control on the Explorer. And G.M. rolled out its Hummer 2, which gets 10 miles to the gallon.