A liter of diesel weighs 0.8508 kilograms, or 1.8757 pounds. A U.S. gallon contains 3.79 liters. Therefore, a gallon of diesel fuel weighs 3.2245 kilograms, or 7.1089 pounds. An Imperial gallon contains 4.546 liters and weighs 3.8677 kilograms, or 8.5269 lbs.

A U.S. gallon is used in the U.S., some Latin American countries and some areas of the Caribbean. The Imperial gallon is used in the U.K., Canada and some areas of the Caribbean. As diesel gets colder, the density increases, and the energy that a gallon contains and the potential miles per gallon the fuel can achieve increases with it. Alternatively, as the temperature rises, the density and potential miles per gallon decreases.