Deionized or Distilled water in a cooling system?

[abbey castro]

You can use any of the Designer Waters like $$$$$ folks use in their cars. Perrier, evian, Fiji, I prefer bling H2O.

 

[deanlemans81]

Most new cars now just specify clean tap water for their coolant mix. The most important thing I beleive is simply proper maintenance of the liquid, ie regular coolant should be replaced every 3 years and long life every 5 years. The problems I see are from coolant that's 10-12 years old still in the rad just because it tests to a -40 freezing point.