http://www.eia.doe.gov/kids/energyfacts/sources/non-renewable/diesel.html
"Diesel fuel is important to America’s economy, quality of life and national security. As a transportation fuel, it offers a wide range of performance, efficiency and safety features. Diesel fuel contains between 18 and 30 percent more energy per gallon than gasoline. Diesel technology also offers a greater power density than other fuels, so it packs more power per volume."