The gauze in the K&N filters is cotton, so you need a cotton safe cleaner. You can't go wrong with the K&N brand. On the cheap, I have had success with a spray cleaner such as Simple Green or Fantastic. It needs to be something designed to cut grease and oil. Saturate, let stand 5 or so minuts, then rinse in as hot of water as you can. Don't use compressed air to clean it, you can blow holes in the cotton gauze. Let it air dry, then reoil. K&N oil comes in spray or a squeeze tube, it has a pink/red dye in it so you only need to apply enough to saturate the cotton to an even color of red/pink.