Date:         Fri, 22 Nov 1996 18:05:31 -0500
Sender:       Vanagon Mailing List <vanagon@vanagon.com>
From:         SyncroHead@aol.com
Subject:      Re: Propylene glycol (Sierra)

In a message dated 96-11-22 11:51:19 EST, wigs@cc.wwu.edu (Neil Wigley)
writes:

<< >- Freezing temperature of these coolants is 10-20 percent higher than
 >ethylene glycol-based coolants.
 >
 >For these reasons, Mazda recommends the use of an ethylene glycol and
 >water mixture in the cooling systems of all Mazda vehicles."
 >
 
 
 What does it mean for one temperature to be 10-20 percent higher than
another?
 
 Neil  >>

Aparently you know something about the nature of the temperature scales we
use and understand that "10-20 percent" higher can not have any precise
meaning.  I suspect that it must have been some non-engineer's guess or
interpretation.

For instance, if the freezing temperature of a coolant was -18 degC, then 20%
higher would be about -14 degC.  On the other hand, in degF the  freezing
temperature would be 0 degF, and of course 20% higher would be, uh,
uh,...still 0 !!   NOT!

Perhaps they meant in an absolute temperature scale like degK (Kelvin).  Then
the coolant would freeze at 255 degK (-18 degC) , and 20% higher would be 306
degK or converted to  33 degC (91 degF) , a drastic 51 degC increase!!   NOT!

See, it all makes NO sense to say that a freezing temperature is some percent
higher or lower than another unless you're talking only about a specific
temperature and scale.

Regards,
Jim Davis
87 GL Syncro
88 GL Wolfsburg