The Bush administration this week missed a large opportunity to improve the country’s energy security. The National Highway Transportation Safety Administration unveiled a complex plan to let the heaviest vehicles continue to guzzle gas while requiring smaller ones to burn less fuel. Rather than a help to American consumers, the proposed new standards prop up outdated thinking from U.S. automakers.

Worse, they prevent states from enacting their own tougher standards for fuel efficiency and pollution controls.

Currently, corporate average fuel economy regulations, called CAFE standards, are divided into two categories: passenger cars and light-duty trucks. New cars must average 27.5 miles a gallon and light trucks 20.7 miles a gallon in 2004 models.

The administration previously increased the standard for light trucks to 22.2 miles a gallon by the 2007 model year. The new plan would raise it to an average of 24 miles a gallon by 2011. Rules for cars are not being changed. From 2008 to 2010 models, automakers would have a choice between the current system and the new size-based system. By 2011 models, only the new system would remain.

Rather than raise the standard for all light trucks, the administration created a new matrix that divides light trucks, a category which includes minivans, SUVs and some vehicles, such as the Subaru Outback and PT Cruiser that most people think of as cars, into six categories. The larger the truck, the less demanding the fuel economy requirements. The largest SUVs, such as the Hummer, are exempted from the rules entirely.

The proposed rule refers specifically to difficulties faced by “full-line manufacturers who have large sales volumes at the larger and heavier end of the light-truck fleet,” a reference to American automakers such as General Motors and Ford which continue to make the largest sport utility vehicles and trucks. A better strategy would be to encourage these companies to make more fuel-efficient models to compete with increasingly popular imports rather than encouraging the status quo – or worse.

According to the National Academy of Sciences, minivans could get more than 36 miles a gallon and light trucks 32 miles a gallon using existing technology. In China, a General Motors executive who oversaw the development of a minivan that got 43 miles to the gallon in city driving quit after his responsibilities were reassigned to a Detroit manager.

Back home, the administration is trying to pass off paltry fuel economy improvements that will save less than a month’s worth of gas over two decades as “good news for American consumers.”

Faced with gas prices over $2.50 a gallon, Americans shouldn’t buy it.