Wehrli Universal 4in Inlet Dry Air Filter (Use w/WCF Kits)Maintenance The cleaning replacement interval depends on your driving conditions. We recommend that you inspect your air filter every 5,000 miles by removing the filter cover and examining the pleats. Keeping your filter cover clean and blowing out your dry air filter with compressed air will help extend the life of the primary filter media. Depending on use conditions we recommend replacing the dry filter every 15 30,000 miles or when you notice that