Andrewh, Instead of addressing the conductivity of distilled water vs non distilled water.
How about addressing your thoughts on the 12 volts in the water/coolant system.
Further, it takes very little to make distilled water conductive. Simply filling it into a cast iron block with its contaniments is enough to make it conductive again.
To me its not a arguement about the coolants conductivity. Its about the alleged 12 Volts in the coolant! mike