I used rhe last of my Meguiars FI to clean my windows today. I was shocked the stuff worked great but the best thing is if you you spray window cleaner on a rag first or if you just spray it on the window you dont have to worry about it harming the finish. I might just start using the FI to clean my windows and I dont use glass cleaner much just dry windows after wash mostly, so the price of it doesnt really matter.