1989 W124 260E
If you have hard deposits no cleaner on the market with shift them .And if they have been on for years it ends up like a film of varnish .So like i said before you can get it back to new again if you use a very fine wire wool. I had work on my car done and the mokeys that did it were not very good , long storey . Well they managed to get over spray on most of the rear windows ..I never saw it till i sat in the car one sunny night looking out the windows ,what a mess . But the wire wool saved the day ..