Probably not specific to a Tesla, but my wipers seem to have made permanent smears on the windscreen. They are only visible when its wet and I have oncoming headlights - but they obscure the view a lot. Cleaning with lots of windscreen spray hasn't shifted it. I've also cleaned the wiper blades. I've read somewhere that cleaning the screen with alcohol will get rid of it - can anyone verify this? Where does one acquire cleaning alcohol?