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Discussion Starter #1
While reviewing the pre-delivery "quality inspection" form in my maintenance journal, I see that the anti-freeze protection is listed as 34 degrees. Surely that cannot be as (a) obviously water does not freeze at 34 degrees anyway and (2) it does sometimes get below freezing here and clearly does in the mountains. What do others see on their inspection checklist?
 

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Discussion Starter #3
Allen Cichanski said:
Check again. A 50/50 mix of antifreeze and water will protect to minus 34F.
Well that makes sense. Probably it was -34. The person who wrote the number in just put "34".
 

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When substances are mixed, the freezing (or melting) point of the mixture is lower than the freezing points of the individual substances. You can protect your car to a much lower temp than -34 by adding more antifreeze. If I recall my phase equilibrium data from my physical chemistry class it is something like 70/30 A.F to water will take it down to -68F. Strangely enough, adding even more A.F. will raise the freezing point!. This optimum mix is known as the eutectic composition and the lowest possible freezing point is the eutectic temp. The worst thing you can do is fill your cooling system with pure antifreeze which if I recall correctly will only protect you to something like +7F!!!. This "depression of freezing point" is the same thing you're trying to achieve when you sprinkle salt on ice. You're trying to create a brine that freezes at a temp lower than the air temp. The standard 50/50 mix is a good compromise of adequate additives in the antifreeze to protect from corrosion of your cooling system and cold weather protection.
 
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