EPA Light-Duty Vehicle Fuel Economy Report, 2012

This 120-page report from the U.S. Environmental Protection Agency details the improvement in fuel economy and parallel decline in carbon dioxide emissions from new cars and light-duty trucks since 1975.

The agency says new technologies that make piston engines more efficient plus the increasing availability of electric and hybrid alternatives are driving the improvements. It also points out that gains would be even better if carmakers weren't also making vehicles that are increasingly heavier and more powerful.

The EPA says average new passenger vehicles since 2007 have become 16% more fuel efficient and emit 13% less carbon dioxide. The report also notes that average fuel economy improved 6% to 23.8 mph from 2011 to 2012, the biggest one-year jump since the agency began calculating the number in 1975.