It illustrates that recent gains in fuel economy have saved the U.S. more than 15 billion gallons of fuel since late 2007. That's the equivalent of all the gas used by vehicles in the U.S. in about 33 days. And it translates to saving about 297 billion pounds of carbon dioxide emissions.
If these gains still sounds modest, consider the longer arc of American fuel economy. Back in 1923, the average fuel economy of all cars, trucks, buses and motorcycles on U.S. roads was about 14 miles per gallon, which sounds surprisingly high when you consider that many vehicles getting only 14 mpgs still ride on the road today. After the 1920s, however, fuel economy actually declined for several decades — gas was cheap, Sivak says, and so we could afford to concentrate on the other things we value about our cars, like power and acceleration.
By 1973, the national average was only about 11.9 mpgs. It steadily increased from there (as oil prices shot up), then plateaued in the 1990s and early 2000s. Now we appear to be making real progress again.