50/50 Ethylene Glycol/Water solution is good down to -34F IIRC.
Even below that it doesn't form solid ice, but more of a slush.
Same should be true of a weaker solution. If you started with 50/50, there isn't anything that should significantly change the concentration.

Kevin
1951 Chevy 3100 work truck
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1929 Ford pickup restored from the ground up. | 1929 Ford Special Coupe (First car)
Busting rust since the mid-60's
If you're smart enough to take it apart, you darn well better be smart enough to put it back together.