The Environmental Protection Agency reported that the average performance of new, 2008 model cars and trucks was 20.8 miles per gallon in 2008, up 0.2 mpg compared with 2007 model year and a 1.5-mpg increase since 2004.
The EPA estimates, found on vehicle window stickers on dealer lots, are based on a combination of pre-sale road tests and projections of likely sales of the new model vehicles. But with people buying smaller, more fuel-efficient vehicles - and fewer SUVs and pickups - those fleet-wide projections were likely to be off the mark, the EPA acknowledged.
The EPA said it was "extremely likely" the 20.8 mpg estimate for 2008 model vehicles is too low.
Honda Motor Co. led the way with a projected 23.6 mpg, followed by Toyota Motor Corp. with 23.4 mpg. Hyundai Motor Co. was third with 22.6 mpg.
Nissan Motor Co. and BMW AG had estimated fuel economies of 21.2 mpg and Volkswagen AG stood at 21 mpg.
Domestic automakers, which have sold a higher mix of trucks and SUVs, were led by General Motors Corp. with an estimated 19.6 mpg. Ford Motor Co. had an estimated 19 mpg and Chrysler LLC came in at 18.9 mpg.
Among individual vehicle segments, hybrids such as the Toyota Prius (46.2 mpg combined), Honda Civic Hybrid (42.9 mpg combined), and Ford Escape Hybrid front-wheel drive SUV (31.5 mpg combined) led their peers.
The EPA noted that the estimates were based on 2008 model year sales projections that were made when gas was selling at $2.50 to $3 a gallon, far below the $3.50 a gallon average during the sales period.
During the year, sales of midsize sport utility vehicles, large SUVs and large pickup trucks have fallen about 15 percent to 25 percent below the auto industry's projections, EPA said.
Fuel-sipping subcompact, compact and midsize cars, meanwhile, have become more popular and vehicles with 4-cylinder engines have gained market share during the span. EPA said the combined factors could lead to higher fuel economy estimates when more sales data is available.
President Bush signed an energy bill last year that requires car makers to meet a fleetwide average of at least 35 miles per gallon by 2020, a 40 percent increase over current standards. Those figures are derived from laboratory testing and the EPA said that average increased to 26 mpg in 2008 compared with 25.7 mpg in 2007.
Environmental groups said the report reflected a lack of good options among many vehicle categories. In the larger truck segments, for example, there was little difference in fuel efficiency among the best performers and the mediocre ones.
"The American people have not had the choice to buy a clean vehicle except for certain sized sedans and the smallest SUVs," said Dan Becker, director of the Safe Climate Campaign for the Center for Auto Safety.
But Charles Territo, a spokesman for the Alliance of Automobile Manufacturers, which represents GM, Toyota, Ford, Chrysler and others, said the report showed the lengthy list of fuel-efficient vehicles on the market.
More than 100 vehicle models offer 30 mpg or better on the highway and they "have become extremely popular recently with the rise in higher gas prices," he said.
Fuel efficiency has become a top selling point at dealerships with the rise in gas prices.