I happen to have a container of pre-diluted "Peak" antifreeze. Peak is a U.S. brand. It uses a type of water called 7732-18-15. I called Peak and they told me it is deionized water. In addition I was told full strength antifreeze, diluted with distilled water would be fine. There's an answer for you if you can believe the manufacturer's tech support line. John Spaur