Correct mix formula - 1/2 water and 1/2 coolant??

Easiest place to find HOAT is at NAPA, Zerex makes it and most NAPAs I've been in have it. When trying to close the drain plug don't get frustrated as it will eventually start to screw in. By the way, it doesn't actually come off the rad, and do use distilled water. Did mine at 100,000 miles.