The average fuel efficiency of U.S. cars and trucks sold in the 2006 model year showed no improvement from the year before at 25.4 miles per gallon, as increased sales of fuel-thirsty cars offset slightly more efficient trucks, according to federal data, the Detroit Free Press reports. The figures -- the first new data in two years -- will likely add to the push in Washington for higher efficiency standards. Several lawmakers want to require U.S. automakers to meet steep annual increases in fuel economy rules. President George W. Bush has said he favors a goal of 4% annual increases through 2017, but has declined so far to back requiring the increases, and automakers have called such hikes unrealistic. Detroit automakers turned in a mixed performance, with flat to lower results for cars and only DaimlerChrysler AG posting a gain in truck efficiency. Toyota Motor Co. and Nissan Motor Co. raised their averages for their North American-built cars and trucks, while Honda Motor Co.'s figures held steady in cars but fell for trucks. According to the Detroit Free Press, the report by the National Highway Traffic Safety Administration estimates automakers' progress toward meeting the standards set by the Corporate Average Fuel Economy program of 27.5 m.p.g. for passenger cars and 21.6 m.p.g. for pickups, vans and SUVs.