New vehicles reached a record-high fuel economy in 2013, the Environmental Protection Agency reported.
In its annual report on fuel economy and carbon-dioxide emissions, the federal agency said Wednesday that 2013 model year vehicles achieved an average of 24.1 miles per gallon. That's up 0.5 mpg from the previous year and an increase of nearly 5 mpg since 2004.
Fuel economy has now increased in eight of the last nine years, according to the report titled "Light-Duty Automotive Technology, Carbon Dioxide Emissions, and Fuel Economy Trends: 1975 through 2014."
Meanwhile, average carbon-dioxide emissions have sunk to a record low of 369 grams per mile.
"Our report shows that today's vehicles are saving Americans money at the pump while emitting fewer greenhouse gases," said EPA Administrator Gina McCarthy. "We are thrilled to see that manufacturers continue to innovate and are bringing technologies to improve fuel economy online even faster than anticipated."
McCarthy attributed the gains in fuel economy to automakers adopting more efficient technologies such as gasoline direct-injection engines, turbochargers and advanced transmissions.
Among the automakers, Mazda vehicles sold in the U.S. averaged the highest fuel economy and lowest greenhouse-gas emissions, the report said. Nissan, meanwhile, achieved the greatest improvement in average fuel economy and greenhouse-gas reductions over the past year.
Looking at the different types of autos sold, sport-utility vehicles and crossovers posted the highest fuel-economy improvement, the report said.
Using a different measurement, auto companies achieved what the federal government calls the Corporate Average Fuel Economy (CAFE) standard of 30.6 miles per gallon in 2013, also a high. The figure is closely watched because of federal rules requiring the industry to reach an average fleet fuel economy of 54.5 miles per gallon in 2025.
Some environmental groups said the EPA report indicates that the auto industry is not moving quickly enough to meet the federal target for 2025.
"The Environmental Protection Agency's fuel efficiency Trends Report demonstrates that the automakers are thumbing their collective noses at the Obama administration's mileage and emissions rules," said Dan Becker, director of the Safe Climate Campaign.
He said preliminary projections by the EPA indicate that fuel economy will barely budge this year.