I have used Windex for years ,,,,, (decades) and it is the very best. In my view, one of the toughest jobs for any cleaner is getting car windows really clear and streak free. A film develops from multiple sources, .... some say from evaporating chemicals in the fabrics and plastics... who knows? it seems to comes from nowhere. I have had great success when preparing windows for a car show using clean, new, white T-shirts and Windex. I soak the first one with Windex until almost dripping and go over every square inch thoroughly. Then a second new, clean T-shirt to dry and polish. Great success! Never use T-shirts, micro fiber cloths etc. that have been previously used with wax. The wax never completely washes out and ruins the window cleaning job.