Why do jet engines use kerosene?

A gas turbine burns fuel continuously in a combustor, not in the intermittent, precisely timed explosions of a piston engine. That difference drives the choice of fuel. Petrol is refined to resist premature ignition under compression, the property measured as octane rating, and pays for it with volatility: it evaporates readily, its vapour ignites at −43 °C, and it is lighter, so a tank of it holds less energy. A turbine has no use for anti-knock behaviour. It wants a fuel that flows reliably, atomises well through a spray nozzle, burns cleanly with a stable flame and carries as much energy per litre as possible. Kerosene, the middle distillate of crude oil between petrol and diesel, fits all of these.

Jet A-1, the standard civil grade outside North America, has a net heating value of about 43.2 MJ/kg and a density of roughly 0.8 kg/L, which means around 34.7 MJ per litre against 32 for petrol. Its flash point is at least 38 °C, so a spill on the ramp does not readily ignite from a spark, and its freezing point is −47 °C or lower, so it stays liquid in a wing tank at −55 °C cruise temperature once the fuel has been warmed slightly by heat exchangers. Jet A, used in the United States, is similar but with a −40 °C freeze point. The fuel also lubricates pumps and fuel-control components, and it absorbs heat from engine oil and hydraulics on its way to the combustor, doubling as a coolant. Additives control static electricity, icing and microbial growth.

Kerosene is cheap to produce because it needs relatively little processing beyond distillation and hydrotreating, and it is available at every airport in the world under a single specification framework, so an aircraft can refuel anywhere without adjusting the engine. Roughly 300 million tonnes are consumed by aviation each year, about 8 % of global oil demand (data as of September 2026). Alternatives exist. Military jets sometimes burn JP-8, which is Jet A-1 with extra additives. Sustainable aviation fuel is chemically similar kerosene made from waste oils, biomass or synthetic routes, blended today up to 50 % and designed to drop in without changing the engine. Hydrogen and batteries are being studied for smaller aircraft, but neither can match the energy that kerosene stores in the wing of a long-haul airliner.