A common question people ask when shopping for a Diesel Truck is why a person would choose a Diesel Truck vs. a Gasoline Truck.
Diesel engines are more efficient than gasoline engines.
A gas engine is only about 20% efficient. That means only 20% of the fuel actually moves the car, and the rest is lost to friction, noise, or engine functions, or it goes out as heat in the exhaust. But diesel engines can reach 40% efficiency and higher. That's why they are so popular for moving heavy vehicles like trucks, where extra fuel really starts to get expensive. (source)
For Example this 2007 Ford F-350 Super-Duty Crew Cab FX4 4X4 Long Bed Diesel Truck being offered for sale by Auto Concepts of Joliet, Illinois in the SW Chicagoland area.