"PaulaJay1" wrote in message ...
In reading the "what oil do you use" thread, a question arose.

What do the letters/numbers after the O 360 mean?

There have been A2B, A3A,A4A,A4M,A1B6 And C1E6 listed.


They are variations on the engine model. They are just assigned (more
or less in sequential fashion) by the engine manufacturer. Lycoming tends
to be more elaborate in their submodels, where the letters describe specific
differences to the engine. Contiental just assigns distinct letters to different
versions.

Here is lycomming's explanation
http://www.lycoming.textron.com/main...modelCode.html