I cleaned my MMM yesterday and had a problem getting some of the black residue off. I used a metal putty knife followed by a plastic putty knife and a stiff brush so I wouldn't take off the paint. It was mostly in a circular area around each of the blades. It is a very light amount. I don't have a pressure washer so I guess I will have to invest in one. Is this possibly mold and it will die after it is exposed to air? I did spray some WD40 on the underside of the deck and put it up for the winter. I will lube it and release the tension on the belt today.