vintage42

Rain-X is a petroleum distillate that makes water bead (not flatten), and does not harm the windshield or anything else. Have used it for 20+ years. It can leave a residue if not polished off, however the residue just makes it work better. Rain-X persists through several regular washes, but windshield cleaners remove it. One thing I don't like is it takes a few minutes to apply and polish, and makes the wipers chatter.

For the moment I prefer Stoner's, which is a glass cleaner that leaves the windshield totally clean and clear, while also slightly making the water bead and run off like Rain-X, and also make the wipers work smoothly. It goes on quickly and wipes dry quickly with microfiber.

Armorall is a water-based polymer that helps, not hurts, whatever it is put on. Have used it for 20+ years, also.