Originally Posted by Kestas
My record is 110K on a Volvo S40 air filter before it tripped a code. Nothing nasty, but you couldn't see light through the media anymore, just as they mention in the manuals. The car ran fine otherwise. I wanted to see how far I can take the air filter because I know people waste their money and change air filters too often. Of course this depends on your local environment and application.
Right. I ran a couple of air filters about that far in my Mazda, with no detectable ill effects, even though it was slightly too old to have closed-loop mixture control. The method of trying to see light through the media used to be the conventional rough check, but some filters nowadays---including my OEM Toyota one---have the pleats packed so close together that you can scarcely see light through them even when new.