I have not touched it in a couple years now, well maybe not that long but pretty long.
Anyways, I have K&N filters and was wondering if there was any particular time frame in which these should be cleaned or replace.
They look fine but a friend said that you can't see the inside where it could be filthy.

I clean mine at every oil change. That may be overkill, but it doesn't take that long.

I clean mine at every oil change. That may be overkill, but it doesn't take that long.

Do you just use that spray stuff or just air blow it?