From what they say(the experts
), stuff like water wetter and Purple ice claim that they can lower operating temps. That doesn't mean they will. The main importance from what I could tell is that the products do many things to help the coolant system run optimally(better then b4 the additive hopefully). I'm no expert(so take this any way you want), but I'd have no problem puting purple ice or water wetter in a stock wrx.