uhhh... whats after run oil?

[BrianG]

After run oil is designed to keep the engine internals from rusting. Without it, the nitro content in the fuel attracts water and causes stuff to rust. Not good.

Air filter oil is not the same at all. This oil is tacky to help traps dirt/dust from entering the engine. Plus, it doesn;t do what after oil is supposed to do. WD-40 works well since it displaces water too.

[TRIVIA]
BTW: What does WD-40 stand for? Water Discplacement formula 40.
[/TRIVIA]

Of course, the simplest solution to prevent this is to run brushless, but you knew that!