Fuel efficiency rose by 1.2 mpg over the previous year, the second largest one-year increase in the past 30 years, the EPA said.
The gain is part of a recent trend. Since 2008, fuel economy has increased by 2.6 mpg or 12 percent. Since 2004, the gain is 4.3 mpg or about 22 percent, the EPA said.
The EPA said data for the year is incomplete, but point to a decrease of 6 grams per mile of carbon dioxide emissions. The average carbon dioxide emissions for model year 2012 vehicles is projected to be 376 grams per mile, a record low, the EPA said.
"Today's new vehicles are cleaner and more fuel efficient than ever, saving American families money at the gas pump and helping to keep the air that we breathe cleaner," said Janet McCabe, Acting Assistant Administrator for EPA's Office of Air and Radiation.
The trend is also expected to continue. The Obama administration has proposed a doubling of U.S fuel efficiency to 54.5 mpg by 2025. That is projected to save consumers an average of $8,000 per vehicle in fuel costs.
"Each year new technologies are coming on line to keep driving these positive trends toward greater and greater efficiency," McCabe said in a statement.