From http://www.eia.doe.gov/kids/energyfacts\sources\non-renewable\diesel.html, June 2006?
Tanker in an Argentina Seaport
Tanker in Ushuaia's (Argentina) seaport.

Source: Stock photography (copyrighted)

A Dirt Scooper and Loader, Loading Dirt in a Dumptruck
Dirt scooper and loader, loading dirt in a dumptruck, redepositing dirt for new runway at the Charlotte Int. airport.

Source: Stock photography (copyrighted)

Rudolf Diesel originally designed the diesel engine to use coal dust as fuel, and then experimented with vegetable oil (biodiesel) before the petroleum industry came out with the product now known as diesel fuel.

The first diesel-engine automobile trip was completed on January 6, 1930. The trip was from Indianapolis to New York City, a distance of nearly 800 miles. This feat helped prove the usefulness of the diesel engine design. It has been used in millions of vehicles since that time.

Diesel Is an Important Fuel

Diesel fuel accounted for about 7% of all energy used in the United States in 2008 and 18% of all petroleum products, the second largest petroleum product after gasoline.

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% more energy per gallon than gasoline. Diesel technology also offers a greater power density than other fuels, so it packs more power per volume.

Diesel Fuel Is Used for Many Tasks

In agriculture, diesel fuels more than two-thirds of all farm equipment in the United States, because diesel engines can perform demanding work. It is also the most widely used fuel for public buses and school buses throughout the United States.

America's construction industry depends on diesel's power. Diesel engines are able to do demanding construction work, like lifting steel beams, digging foundations and trenches, drilling wells, paving roads and moving soil — safely and efficiently. Diesel also powers the movement of America's freight in trucks, trains, boats and barges; 94% of our goods are shipped using diesel-powered vehicles.

The military also uses diesel for fighting vehicles like tanks and trucks, because diesel fuel is less flammable and explosive and less likely to stall than gasoline.