1933 coolant "water"

[rotorwrench]

Now days you have reverse osmosis as well as distilation. While the RO water might be preferable, it is still basically H2O but just a cleaner version with minerals and other molecules removed. Water, by itself, is not as effective as a coolant mix that will allow heat transfer and prevent corrosion plus be a safer against freezing in cold weather.

These were inexpensive cars for the day so folks weren't all that worried about whether the engine block would rust. They may have worried about it freezing in the winter a lot more than any possible corrosion. Folks in rural America or about any other country for that matter, basically used what was at hand. If it overheated out in the country somewhere, the water from a mud puddle may have been poured in there.