Automobiles in the United States have made great strides with regards to fuel efficiency over the years. Since 1975, the average miles per gallon of vehicles sold in the United States has nearly doubled – from 13.1 to 24.1. All the while, horsepower has increased nearly 66%, 137-227, during the same time period.
The interactive chart below has all of the data from the Light Duty Fuel Economy Trends report from the United States EPA. Average horsepower is the orange line and the average fuel economy is the blue line. Noteworthy is the steady drop in fuel economy from 1998 through 2004, while horsepower is increasing sharply.