U.S. auto makers engineered big gains in fuel efficiency during the past decade, but the pace is slowing as consumers snap up more pickup trucks and sport-utility vehicles. The U.S. Environmental Protection Agency on Wednesday estimated fuel efficiency of 2014 vehicles would rise just one-tenth of a mile per gallon from 2013, a sharp slowdown from the half mile a gallon increase the agency calculated between 2012 and 2013. The EPA said cars and light trucks produced in 2013 averaged 24.1 mpg, a record since the government began keeping tally in 1975.