SAN JOSE, Calif. — Drivers could save as much as $2,000 a year on gas if they bought the most fuel-efficient vehicle in a segment compared with the one with the worst mileage, a consumer group said yesterday.

The owner of a Honda Insight, a two-seat hybrid, would spend $1,850 a year less at the pump than the driver of a two-seat Mercedes-Benz SL600.

While the Insight and the SL600 are very different vehicles, the Consumer Federation of America said consumers could save money even when choosing among vehicles that are closer comparisons.

A driver of a midsize sport utility vehicle would save $1,707 a year by choosing a To-yota Highlander hybrid instead of a Jeep Grand Cherokee, the group said. The gas-cost savings ranged from $307 for the consumer who picked the highest-mileage minivan (Honda Odyssey) instead of several others, the Chevrolet Uplander AWD, Ford Freestar 4.2L and Toyota Sienna 4WD, to $1,995 for the truck driver who bought a Toyota Tundra 4WD instead of a Dodge Ram 8.3L.

Consumers "simply aren't aware" that such choices exist within each segment, said Jack Gillis, the federation's public affairs director. The Washington, D.C., advocacy group offered a new way to look at fuel economy.

It created a four-tier scale that rates vehicles getting at least 40 mpg as "excellent," those in the 30-to-39-mpg range as "good," those in the 20-to-29-mpg range as "fair" and those that get less than 20 mpg as "poor."

Of the 1,079 models it evaluated, 42 earned the "excellent" or "good" rating. That leaves 611 vehicles that get fuel economy rated as "fair" and 426 vehicles that get mileage rated as "poor."

Gillis, author of the annual "The Car Book," which rates vehicles on safety and other factors, said the group will use the scale in its publications and press releases, and will encourage the Environmental Protection Agency, which is in process of revising its fuel-economy guidelines, to adopt it.

Buyers are paying more attention to fuel-economy estimates lately as gasoline prices — which climbed over $3 a gallon last year — remain well above $2 a gallon.

Last year, Consumer Reports magazine said tests of 303 vehicles showed 90 percent got worse mileage than promised by government fuel-economy ratings.

In January, the EPA said it would reduce those ratings by 5 percent to 30 percent, depending on type of vehicle and driving condition, to bring them closer to real-world fuel economy.

Those changes are expected to start with 2008 models.