Here's my two cents.... first I would try a very mild solution of clr and spray on allowing about 10 seconds to "penetrate", don't scrub, use a sponge and have a hose close by to wash off thoroughly, be sure to get around the door edge to wash out or wipe out any trapped solution against rubber. If it is what I suspect this should clean it up. If it doesn't, do follow up with a mild degreaser like Fanstatic, same time frame and method. I doubt the latter will be useful, but cover all the bases (acid and basic). Still no results? Then do a VERY quick non abrasive compound compound, or at the very least a non abrasive polish. You won't want to compound or polish the aluminum, it will get very shiny and stand out. With that in mild, be sure to tape behind the door edge but over the rubber and tape off the aluminum, if any residue is left, goof off can be used to remove it. Because this plastic looks, to me at least, to be polycarbonate, would be likely quite soft, so don't even use a compound or polish pad, use a wax pad. Use about a fat nickels worth and gently distribute with your finger (as opposed to wiping on target area like one would w paint). I wouldn't go much past half speed, regardless of brand, PC, Flex, Griot's, etc. See what the first pass does before hitting it again. I would suggest using a mifcofiber better than 400gsm (800+ would be ideal just cause it is shaggier) to remove residue, and DON't let residue dry, and don't use a terry towel or other household towel. (This is all assuming you are using 3" polisher, but of course it can all be done by hand). If you are a sonax guy, the first steps can be substituted with a few sprites of Fallout Cleaner and high gsm microfiber, but be quick, don't let it dry, and have a hose ready. The liquid methods may knock it out, the polisher method absolutely will. Any questions, lmk, but for sure let us know how it works out. Don't forget to follow up with a decent wax, whatever brand you prefer, in two very thin coats, again, only use microfiber.
