Hey, I just put some prestone radiator cleaner in my radiator. Says its fine for aluminum radiators but I was wondering if it would be safe to use for a little while because you're supposed to run it through the radiator for 3-6 hours(in a car im guessing) on and off use is OK it says. Just wondering if it would likely overheat. Also, which coolant to use??? Also, are the radiator guards worth buying???