The Obama administration in May announced that the mileage of cars and light trucks sold in the U.S. must rise from the current 25 miles per gallon to 35.5 mpg by 2016. That’s a 40 percent improvement. But perhaps a more meaningful measure of fuel efficiency is fuel consumption per distance traveled. People who drive an average vehicle for 100 miles a week will see their weekly gas usage drop from four gallons to 2.8 gallons frut—a 30 percent reduction in both expenses and carbon dioxide emissions. And though significant, the efficiency gains will not be enough to bring the U.S. in line with what vehicles sold in Japan and Europe already consume now.