Randall wrote :
>
>> Antifreeze/water is actually not as good a coolant as pure water,
>> the main reason for using antifreeze is because of the corrosion
>> inhibitors in it. These do wear out over time, so it needs to be
>> changed every 2 years. Since you live in SD (so don't need
>> freeze protection), don't use more than about 1/3 anti-freeze to
>> 2/3 distilled water.
To which Jack McGahey replied :
> Not sure what you mean by "not as good a coolant" - surely you
> don't mean antifreeze/water doesn't have a higher boiling point
> than pure water - it most definitely does. The principle by which
> this works (freezing point depression/boiling point elevation)
> also explains why you don't ever want more then 50%
> antifreeze - beyond that point the freezing point comes back up
> and the boiling point comes back down. You need the right mixture
> to get the best protection from freezing and boiling.
I meant not as good a coolant in the sense that a given engine will run
cooler under given conditions with pure water than with a 50/50 glycol/water
mix (with a fully open or non-functioning thermostat of course). I'm not
sure of the exact reason, but my understanding is that it's because glycol
doesn't conduct heat as well.
I did actually mean to mention the elevation of boiling point, although I
don't agree that it comes back down as the concentration increases. Pure EG
doesn't boil until something like 200C, there is a smooth (although not
linear) increase in boiling point from pure water to pure EG. FWIW, I have
actually tried running pure EG to prevent boil-over, it got me home but I
wouldn't recommend it. The engine swallowed a valve a few years later,
probably because of the lean mixture that was causing the overheating.
The freezing point does come back up, minimum freezing temp (about -65F) is
at about 60% EG / 40% water.
I also meant to say "the main reason for using anti-freeze in climates where
temperatures never go below freezing...", obviously most listers will need
antifreeze to prevent freezing ...
Randall
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