Professor Fate said

Yes, daily drivers generally benefit from a 50/50 mix (regardless of ambient temps), but in situations where anti-freeze is not allowed, running straight water aggravates the corrosion problem, and electrolysis becomes more of a concern- especially with the increasing use of dissimilar metals in the cooling system. Think: iron blocks, aluminum heads, aluminum radiators, etc. Generally, the "softer" metals are the ones most subject to issues (think how common it is to get leakage due to corroded coolant passages in SB timing covers, for instance). So, when an even lighter metal is introduced into the system, it becomes the first to react. This is why anode rods in home water heaters use aluminum or magnesium as a sacrificial material. Zinc is more reactive yet, but not suitable for potable water systems- but is great for other instances, like freshwater/saltwater cooling in marine environments. That technology is just being borrowed to use in the OP's situation.

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