A catalytic, high-pressure process flexible enough to produce either of the two major light fuels—high octane gasoline or aviation jet fuel. It proceeds by two main reactions: adding hydrogen to molecules too massive and complex for gasoline and then cracking them to the required fuels. The process is carried out by passing oil feed together with hydrogen at high pressure (1000–2500 lb/in.² gage or 7–17 megapascals) and moderate temperatures (500–750°F or 260–400°C) into contact with a bifunctional catalyst, comprising an acidic solid and a hydrogenating metal component. Gasoline of high octane number is produced, both directly and through a subsequent step such as catalytic reforming; jet fuels may also be manufactured simply by changing conditions with the same catalysts. The process is characterized by a long catalyst life (2–4 years), though a slow decline in activity occurs, caused by the deposition of carbonaceous material on the catalyst. Regeneration at intervals by burning off these deposits restores the activity, but eventually the catalyst porosity is destroyed and it must be replaced.