Load of bollocks, 6061 is Dural not aluminium and rots like hell if not PTd. If it is clad it has a very thin layer of aluminium on it's outer faces. Once that is penetrated it will rot PDQ if exposed to moisture. Waterless coolant is fine but the one i have seen at £65.00 a gallon, does not make me want to go out buy three gallons of it to do a coolant change.