LOS ANGELES — The conventional wisdom that ultra-environmental vehicles must be either tiny and impractical or festooned with expensive hybrid technology got a kick in the teeth as the diesel-powered Volkswagen Jetta TDI won the Green Car of the Year award Thursday at the Los Angeles auto show.

“The Jetta TDI epitomizes what the Green Car of the Year honor is all about,” said Ron Cogan, editor and publisher of Green Car Journal, which presents the award. “It raises the bar significantly in environmental performance” with EPA fuel economy ratings of 31 mpg in the city and 41 mpg on the highway.

The Jetta TDI achieves “the kind of fuel efficiency offered by gasoline-electric hybrids but in a more affordable way,” Cogan said. Prices for the 2009 Jetta TDI start at $21,990 for the sedan and $23,590 for the station wagon.

Diesels have long been the vehicle of choice for fuel efficiency and reduced emissions in Europe, where they account for more than half of new-car sales. Diesels have languished in the United States, however, accounting for less than 1 percent of car sales.

The Jetta TDI beat the BMW 335d diesel, Ford Fusion hybrid, Saturn two-mode hybrid and Smart ForTwo city car for the award.

In addition to the editors of Green Car Journal, judges for the award include Jay Leno; racing legend Carroll Shelby; the top officials at the Sierra Club and National Resources Defense Council, and oceanographer and environmentalist Jean-Michel Cousteau.

The 2008 Chevrolet Tahoe hybrid SUV won the award a year ago, a first step in the mainstreaming of green technology, which in the United States had traditionally only been seen in small vehicles.

A number of European automakers offer fuel-efficient new diesels in the United States, but only the Jetta meets the emissions standards of all 50 states without expensive and complicated emissions technology.

Ford and GM sell high volumes of diesels in Europe but do not offer them in the United States. GM plans to introduce a new diesel V-8 for sale in light trucks and possibly cars in 2010.

The Jetta TDI sedan and wagon went on sale in August. VW has sold about 8,000 so far, and the TDI diesel model accounts for 80 percent of the wagon’s sales, VW of America president Stefan Jacoby said.

“We are confident the popularity of clean diesels will continue to drive” sales of vehicles with the technology, Jacoby said. VW plans to offer the technology in a wide range of its models.