Distilled water by itself is corrosive but when it's mixed with anti-freeze, it is not. There should be no debate.

This was explained over and over by the great Frank King who was the Techical Editor for the Star magazine for decades.

On the other hand, tap water varies tremendously depending on where you live. In Minnesota we had deep wells that produced hard and ancient water. In Arizona we get a lot of water that is stored in aquifers. The water in Arizona is so bad I had an RO system installed in my new home. The water here actually looks oily.

Bud