Trying to finally fix my radiator problem. One question I forgot to ask the board was if it was ok to use tap water in my radiator or should I use distilled? I'm using the BMW phosphate free antifreeze and doing a 50% dilution. I know I could use tap water if I had to (I've certainly done that in other cars) but I want to do what's BEST. My bentley is in storage and can't get in touch with my usual BMW resource buddy. The radiator is "bone dry" right now...would that make a difference? TIA