When oil prices soar through the ceiling, and gas-guzzling Hummers go out of style, there's a simple solution for local governments: Switch their fleets over to hybrid cars.

Unfortunately, it's TOO simple.

The newest wave of hybrid cars drinks considerably more gasoline than the first one did. That's because automakers are in some cases using hybrid technology to increase vehicle performance rather than fuel economy. Take Honda's hybridized Accord. It gets just 29 miles per gallon in town--good compared with some cars, but only a tad better than non-hybrid versions of the Accord.

Early hybrids such as Honda's Insight and Toyota's Prius earned warm- and-fuzzy reputations for greenness. They deserved it: They got upwards of 60 mpg by running on a mix of gasoline and an electric battery that continuously recharges itself.

Impressed, states and cities began buying hybrids for their fleets. They also promoted the cars heavily to consumers. California, Florida, Georgia and Virginia let hybrid drivers ride solo in HOV lanes. Albuquerque lets hybrid drivers park at city meters for free. Colorado, Maine, Oregon and Pennsylvania offer residents big tax breaks for buying hybrids.

The trouble is, most of these enticements still treat hybrids as though all have been created equal. This creates some odd disparities. Colorado, for example, offers a $2,936 tax credit for buying the hybrid Accord. But if you buy a gasoline-powered Honda Civic that gets even better mileage, you don't receive any credit at all.

Florida lets the hybrid version of GM's Silverado pickup ride in HOV lanes--despite the truck's mediocre 20 mpg rating on the highway. Critics call the Silverado a "hollow hybrid." It uses the technology primarily to power electricity outlets. "It's perfect if you're camping or tailgating and want to plug in a TV set," says Jim Kliesch, of the American Council for an Energy-Efficient Economy. "But it won't save much fuel."

Now that automakers have started fooling around with the technology and terminology of hybrids, it's time for a second look. The energy bill Congress passed in July suggests one path forward. The new law calculates federal tax credits by taking into account how much fuel a hybrid saves compared with comparable cars of conventional design. But here's an idea that might work even better: Reward desired outcomes-- say, gas mileage of 40 mpg--and don't worry about the technology used to obtain it.