I love the Rain-X brand. $3 a gallon at Walmart.
Automatically coats your windshield with Rain-X. That stuff is great while driving in a rainstorm. You don't even need your windshield wipers.
I was just going to post about the Rain-X brand. I’ve gone 50 miles at a time in driving rain with no wipers. Well worth the money
I have a friend who’a an amateur chemist. He tried making his own once and stripped the paint off his roof.