There is projected to be an increasing demand for the middle distillate (350-640°F) boiling range portion of the crude oil barrel. This is due to increased vehicle dieselization and increased demand for kerosine type jet fuel. To improve jet fuel supply, specifications have been relaxed permitting the use of diesel fuel boiling range material. Since no similar change has been made in diesel fuel specifications, its potential availability is reduced. Increases in the 90% recovery temperature to 680°F to improve diesel fuel supply in Europe have already been made. Similar changes should be made in the U.S. A review of the performance of fuels indicates that there should be no substantial adverse effects when these higher boiling fuels are used. This change could provide as much as 4-1/2% (on crude) more distillate.