Light and heavy trucks offered increased fuel efficiency over similar sized gasoline powered engines. In 2011, diesel fuel engines have been improved to offer cleaner burning fuels and increased exhaust technology to meet emissions standards regulated by the Environmental Protection Agency.
The U.S. Government's comparison of diesel and gasoline fueled engines shows an increased fuel efficiency in diesel of between 30 and 35 percent. In part, this has been made possible by fuel technology, such as ultra low sulfur and biodiesel.
Diesel fuel burns to create more heat, around 147,000 British thermal Units (BTUs) of energy per gallon compared to 125,000 BTUs per gallon for gasoline fuels. Less diesel fuel is needed to reach operating temperatures than gasoline, resulting in increased miles per gallon of fuel.
Diesel fuel truck engines use a direct fuel injection system, which also increases mpg's over gasoline engines. As fuel is passed directly into the cylinder in diesel systems, the engine has less wasted and unburned fuel in its system compared to gasoline engines, meaning increased mpg's.
