Mike, I tried Armor all, and Mothers. They didn't touch it. I tried the Kaboom only because the Honda is not quite as rare as the XF, lol. The crud on this wheel was the same all around. But ONLY on the spare. Maybe the P.O cleaned the wheels on the ground, but never touched the spare? Maybe the spare had the cover on it for years, and never dried out? The P.O was pretty meticulous about things. The engine compartment looks like brand new.