Plain English Meaning
A type of aircraft fuel that works the same as the common blue 100LL fuel but contains even less lead. Engines approved for 100LL can use it without any changes.
Full Definition
An aviation gasoline (avgas) grade with an octane rating of 100 and a reduced tetraethyl lead content compared to 100LL. It is dyed blue, like 100LL, and is approved as a direct replacement in piston aircraft engines that are certified for 100LL.
Context Anchor
Seen in fuel grade discussions, aircraft fuel placards, fuel truck markings, and pilot operating handbook .