There is some misinformation on this list, from time to time. Most of the
comments about water being a better heat transfer agent are correct, however
the comments about PG not being as good a heat transfer agent as EG are
somewhat misleading.
I manage an engineering organization including a number of PhD. Chemical
Engineers. We had the heat transfer discussion about EG versus PG at lunch one
day. On the way back from Mineral Wells last August, my Miata was overheating
towing my tire trailer at any speed over 8O MPH. I am running PG. That evening,
one of the engineers ran some very sophisticated and highly accurate heat
transfer models and found the heat transfer difference is insignificant.
Water is best, but as others stated, it doesn't have the boiling point
suppression, coorsion inhibiters, lubricants, and some other characteristics
one might occasionally find useful. Also contrary to myth, there are a variety
of brands of PG being marketed right now that have some characteristics one
might find useful in their automoble, versus being safe for your pet to drink.
.
EG is used mostly because it is CHEAP, not because it is better. PG costs more
and tends to be more expensive in the winter because it is used for airplane
deicing. The US banned EG a number of years ago for de-icing, although it is
still used in Canada and other countries.
To answer someone's question about helping cool the engine while towing, you
might also want to consider adding a separate oil cooler. This helped more than
I thought it would on a tow vehicle once.
Jim Hedderick
Houston, Texas
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