This is what the cabin air filter of my 2003 Toyota Corolla looks like after ~94,000 miles. That’s way overdue!
The one on the right is a new Bosch cabin air filter. I bought it at Kragen for a little over $17 with tax, then took 5 minutes to swap it was the old, filthy cabin air filter.[1. How to Change the Cabin Air Filter in a Toyota (wikiHow)]
From now on, it goes every 10,000 miles.
Whoa, I was warned back in October 2007 by Clever Dude. Unbelievable!