JohnZ

New car owner's manuals (at least for DaimlerChrysler and Mercedes-Benz) are VERY specific about using ONLY distilled water in the cooling system, with possible invalidation of the powertrain warranty if tap water is used instead. That's good enough for me.

rgs

I agree that if the vehicle warranty is at issue, then follow the manufacturer's requirements by all means, but last night I looked up the cooling system recommendations from the owner's manuals for several of my vehicles. The only one to mention distilled water was a 1998 GM product and it said "...use a mixture of one-half clean water (preferrably distilled) and one-half DEX-COOL coolant...." There is no mention of invalidating warranties with using tap water in it.

I reviewed manuals for five other vehicles; Ford, Mazda, Nissan, Dodge, Chevy. None of these owners manuals make mention of distilled water. One, the Mazda, mentions using "soft (demineralized) water" which, as I recommended in my first post, is what comes from softened tap water.

If there is other wording in someone else's manuals to the contrary, please let us know, but my GM and other manufacturer warranties are intact using softened water from the tap.

I believe my posts are being mis-interpreted (one of the problems with words alone). I described the processes of water treatment and the problems of using ONLY distilled water in a radiator for everyone's background information. Correct me if I'm wrong, but I believe everyone agrees with me that using ONLY distilled water without additives, such as anti-freeze to raise the conductivity is a bad idea. I am involved with racing and have dealt with numerous cooling issues on a variety of race cars. We rarely use antifreeze. We have to be conscious of these other issues that the normal street driver can remain oblivious of.

On the opinion of using distilled water versus softened water from the tap to mix with anti-freeze, I have no issue with using distilled water once it is mixed with antifreeze (treated as I put it in the first line of my first post). It is just a waste of time and money in my opinion. Others feel it is worth the extra. That is their opinion.

I do have issue with using distilled water with Water Wetter. Typically water wetter is an 8oz bottle. Even if it has a high conductivity, there is not enough volume to appreciably raise the conductivity of a 2 gallon cooling system from the 0 uS of distilled water to a safe level (around 200 uS).