After getting an oil change yesterday, the people there said my air filter was pretty dirty and it needed to be changed soon. They didn't have a replacement, but said the one I need is like 50$. I was wondering if you really need to replace the air filter, or if you can just clean it. If you can clean it, that means those people took out my air filter, saw how dirty it was, and then put it right back in. That seems kinda strange to me. That's like a doctor doing an operation on someone, and he checks everything else out while he's in there, sees there's a kidney stone in the kidney and leaves it there and tells you later that you should get a new kidney soon.