I use Simple Green and a bucket deep enough to submerge the filter. I do dilute it maybe a cup to couple gallon and half or so. I submerge for a few minutes, then use a very soft brush on the outside, rinse from inside with no pressure, submerge again for a few minutes, rinse from inside with no pressure and then let air dry for a day. I have second filter always clean, oiled and ready to install.