Definition
A classification that identifies the type of aviation fuel by its performance characteristics, primarily its octane rating and additives. Aviation gasoline (avgas) grades are standardized and color-coded so pilots and line crews can confirm the correct fuel is being used. Common piston-engine grades include 80 (red), 100 (green), and 100LL (blue, low-lead), each with specific octane ratings and lead content. Turbine-engine aircraft use jet fuel grades such as Jet A and Jet A-1, which are kerosene-based and not interchangeable with avgas.
Plain English
The specific type of fuel an airplane is designed to run on. Each grade has its own performance rating and color so it can be identified at the pump and in the tank.
Context Anchor
A pilot checks fuel grade during preflight planning, at the fuel pump, on fuel placards, and in the aircraft’s operating information.
Derivation
Grade' comes from the Latin 'gradus,' meaning step or rank. A fuel grade ranks fuel by quality and performance, so each 'step' on the scale tells you how the fuel will behave in the engine.
Why Pilots Care
Selecting the wrong fuel grade risks engine damage from detonation or power loss during flight.
Intuition Check
Do not read “fuel grade” as meaning “fuel quality” or “how clean the fuel is.” Here, “grade” means the approved rating or class of fuel the engine is allowed to use.
Example Sentence 1
Before fueling, the pilot checked the placard and confirmed the fuel grade was 100LL.
Example Sentence 2
A lower fuel grade than specified can cause knocking during high-power climbs.