WE HAVE BEEN USING DISTILLED WATER FOR COMPLETE FLUSHES AND ADDING COOLANT FOR 20 YEARS. OUR WATER HAS HEAVY RUST. WE WERE REPLACING RADIATORS WAY TOO SOON UNTIL WE STARTED USING THE DISTILLED. WE USE THE COOLANT TEST STRIPS FROM DANA AND USE NAPA KOOL # 4056 ... Login to read more.