from:
http://www.amsdj.com/products/filter.htm
The service life of AMSOIL
Air Filters can be extended indefinitely when the following instructions are performed. For normal driving conditions, service AMSOIL Air Filters every 25,000 miles or one year, whichever comes first.
1. Remove air filter from air filter housing.
2. Wipe housing free of dirt and debris.
3. Carefully remove polyurethane foam from metal cage of AMSOIL Air Filter (Note: foam is not removable on planar-style filters).
4. Wash polyurethane foam in detergent and water or in parts cleaning solution. Rinse in clean water and allow foam to dry completely.
5. Apply AMSOIL Foam Filter Oil liberally on polyurethane foam. Squeeze foam repeatedly until oil penetrates its entire thickness. (AMSOIL Foam Filter Oil is specifically formulated for AMSOIL Air Filters and is designed to trap and hold dirt effectively, even in temperature extremes.)
6. Blot excess oil from polyurethane foam and reinstall foam on metal cage.
7. Reinstall AMSOIL Air Filter into air filter housing. Be sure the label is attached to the outside of the filter housing.