DONT use Rain-X on clear vinyl .......
Most of the manufacturers warn against its use on vinyl and vinyl windows. It slowly dissolves the plasticizers (or the surface coating polymers that help contain the plasticizers such as in Strataglass), and eventually 'fogs' the surface when it causes the surface to become visibly 'orange-peeled', leaves it 'gummy', ... all this takes time but the end result is: you will have to replace the vinyl windows much sooner than if you dont use Rain-X or similar products. Ditto with most 'water repellents', including those that your spray-on to Sunbrella. (Apseal 303 Repellent, etc.) ... I use APseal 303 UV *Protectant* on my convertible tops, and the vinyl windows, etc. with no apparent degradation. Dont confuse 303 UV *Protectant* with 303 *Repellent* - they are very different products.