Remove filter and inspect for damage or wear.  Spray liberal amount of cleaner solution on the filter and let it sit for 8-10 minutes to allow the cleaner to work.  Rinse filter gently with water.  DO NOT use high pressure nozzles or a pressure washer.  Normal water pressure from a sink or hose is all that is needed.  Rinse filter until you no longer see soal residue rinsing from the filter.  Place the filter in the sun or someplace dry.  You need to allow enough time for the filter to dry completely.  NEVER use compressed air to dry filters.  Once the filter is dry apply the filter oil.  This is done by applying a bead of oil around the circumference of the filter about 1/4 way down from each edge.  Let the filter sir for approximately 1 hour and the oil should have wicked through the filter to cover the un-oiled areas.  If there are areas where the oil didn't cover well, put a few drops in that area to complete oiling. Your filter is now ready to re-install.