I just finished using the Aluminex products on a "new to me sled". Heavy oxidation from UV through a garage window I'm guessing, as it was only in the water about 20 days. Anyway, used the Clean and Shine first and it did next to nothing, so then tried the Hull and Bottom cleaner. This went right to work, diluted as directed. In fact so fast, I couldn't control it when I sprayed it on. Decided to go by the instructions and brush it on (imagine that?) and did much better, but it still scared the **** out of me because it literally white washed the aluminum. Keep in mind, this was a first for me, so take nothing I say as having experience! In the end, I went over it completely afterwards with Flitz and it came out great, or as good as I am capable of. Even when there was some streaking from the Aluminex. My thoughts would be that if you only did the waterline, you may see a transition between old and new.