Diesel fuel weighs about 7.1 pounds per gallon, so a liter, of which there are 3.8 in a gallon, would weigh about 1.9 pounds. --- Since a litre (liter) is a metric measure, …best to keep the whole answer in metric, don't you think? A litre (liter) of diesel fuel weighs 832grams, or 0.832kg.