Gas oil is one of the fractions (parts) into which petroleum is divided by distillation. Gas oil comes from about the “middle” of the still. It is heavier than gasoline and kerosene and lighter than the lube distillate from which lubricating oils and waxes are made. The name gas oil comes from the use of this oil in the production of gas fuel. Gas oil is converted into such lighter petroleum fractions as gasoline and chemicals. It is also used for diesel oil and fuel oil. See also Petroleum (Refining petroleum) .