OK, this isn't your regular convertible top cleaning question, this is about stains. I have a 2006 M3 convertible that I've kept in very good condition using 303 cleaner and protectant. Something began staining the top in isolated places near the rear window (note that this is the part that folds down first&lowest when the top folds away--relevant to my diagnosis of oil stains). Since the top is black, I cannot tell what color the stain is, but it looks darker and has a somewhat gummy feel, though it is deeply absorbed in the canvas material. I've used the cleaner with bristle and nylon brushes, I've tried weak solvents (isopropanol) and I've tried Goof Off! cleaner. None of them work on removing these stains, at least not at the amount of scrubbing that I am comfortable with. The newest spot came yesterday, after my car sat in the garage overnight with the top down. I'm fairly sure now that this is oil from the hydraulic system that occasionally leaks out into the tray that holds the top. Question is, how can I clean the stuff out? The top is in good shape after 9+ years, and I don't want to get a new one if I can do something to remove this stuff, but I don't want to discolor it with solvents or excess abrasion. BTW, I've also looked at the pump (which is below the tray in a separate part of the trunk) and it isn't showing any signs of leaks, otherwise I'd have fixed them before this.