Definition
A petroleum-based fuel, heavier and less volatile than gasoline, used in compression-ignition engines. In aviation, diesel fuel (or its close relative, Jet A) is burned in modern aircraft diesel engines that ignite the fuel by the heat of highly compressed air rather than by a spark plug.
Plain English
A heavier, oilier fuel than avgas. The engine squeezes air until it is hot enough to ignite the fuel on its own — no spark needed.
Context Anchor
Seen in aircraft fuel system descriptions, engine operating information, and refueling procedures for aircraft equipped with diesel engines.
Derivation
Named after Rudolf Diesel, the German engineer who in the 1890s developed the compression-ignition engine that runs on this type of fuel.
Why Pilots Care
Some modern aircraft engines run on diesel fuel or Jet-A, offering better fuel economy and access to automotive fuel supplies in remote areas.
Grounding Statement
In a diesel engine, the air is squeezed until it gets hot enough for the injected fuel to burn.
Intuition Check
Diesel fuel does not mean “any fuel for an engine.” It means fuel intended for a diesel-type, compression-ignition engine, and it must match the aircraft’s approved fuel requirements.
Example Sentence 1
The flight school's new trainer uses a diesel engine, so it is fueled with Jet A rather than 100LL avgas.
Example Sentence 2
Switching to diesel fuel allowed the aircraft to operate on widely available truck fuel at smaller airports.