We use Nu-Brite as well, everyone has their own prefferrence as to wich one according to job at hand. I use the purple on outdoor coils, and the green slf rinsing on indoor coils. Both work well and in my area we get a lot of oily residue as well as cotton wood. I do need to seperate the two coils to get the build up from in between them. Rinsing with a hose and spray nossil. Seen too many finns closed due to high pressure!