WASHINGTON (AP) – The average fuel economy of 2006 model year vehicles remained constant compared with last year, the government reported Monday.

The Environmental Protection Agency said in its annual report, based on sales projections provided by automakers, that the estimated average fuel economy for 2006 vehicles was 21 miles per gallon, the same as 2005 models.

Honda Motor Co. had the highest fuel economy rating by manufacturer, 24.2 mpg, followed by Toyota Motor Corp., with a 23.8 mpg average. But both Japanese automakers saw their averages drop from the previous year as they placed more of an emphasis on larger vehicles.

DaimlerChrylser AG had the lowest fuel economy rating – 19.1 mpg – followed by Ford Motor Co., which improved half a percentage point to reach 19.7 mpg. General Motors Corp. also showed improvements, posting a 20.5 mpg average, but environmental groups said they were disappointed by overall results.

“The more things seem to change in the world in terms gas prices and energy crises, the more things seem to stay the same in the auto industry,” said David Friedman, research director for the Clean Vehicles Program at the Union of Concerned Scientists.

The EPA report showed fuel economy averages 5 percent below the peak of 22.1 mpg in 1987-88.

Among vehicle type, passenger cars averaged 24.6 mpg in 2006 – down from 25 mpg in 2005. SUVs averaged 18.5 mpg, an increase of 0.2 mpg, and pickups rose by 0.1 mpg to average 17 mpg.

The amount of miles a motorist gets on a gallon of gas has declined slightly as consumers have bought more sport utility vehicles and pickup trucks and, in general, vehicles have improved in acceleration and become heavier.

In 1987, about 28 percent of vehicle sales were light trucks, which include pickups, SUVs and vans; about half of the vehicles sold today fall into that category. The average vehicle weight has increased from 3,220 pounds in 1987 to 4,142 today, while the average 0-to-60 acceleration time has fallen from 13.1 seconds in 1987 to 9.7 seconds in 2006.

Charles Territo, a spokesman for the Alliance of Automobile Manufacturers, said nearly every new model offers fuel-saving technologies such as engines equipped with variable valve timing and cylinder deactivation.

Consumers can also choose from more than 100 models attaining 30 mpg or better or more than 40 alternate fuel vehicles such as hybrids, diesels or vehicles capable of running on 85 percent ethanol blends.

“Manufacturers are always looking at ways of bringing new fuel efficient technologies to market,” Territo said. “The challenge is creating vehicles that continue to meet consumers’ needs while also providing increased fuel efficiency.”

Gas-electric hybrid vehicles were among the leaders in vehicle nameplates by class. The Honda Civic hybrid led among compact cars with a combined fuel economy rating of 49.8 mpg while the Toyota Prius led midsize sedans with 55.3 mpg. A version of the Ford Escape hybrid led midsize SUVs with a 33.3 mpg average.