Re: More Antifreeze

[MEL1523@ACS.TAMU.EDU]

;> I think that the Sierra product uses propylene (sp?) glycol as opposed to
;> etheylene glycol. If the product is pure propylene glycol, it is safe to
;> ingest. However, it seems like there must also be additives that wouldn't be
;> safe.>
;> I thought that propylene glycol was only usable in high flow, non-pressurized
;> systems...?
;>
;I was working at NAPA on Saturday, and had a guy come in to buy some
;antifreeze.  "You guys carry Sierra?"  "No sir, we carry this NAPA crap, I use
;it in all my cars."  "Good thing.  I've put Sierra in three cars, and each car
;blew a water pump three weeks after I put the stuff in."
;Does this have anything to do with the propylene glycol business?  I'd never
;heard anything about Sierra, good or bad, so maybe this guy just had bad luck?

Yes, Sierra uses Propylene glycol as the main ingredient.  Audi manuals and 
stickers under the hood say...use an ethylene glycol based coolant.  
Propylene glycol has very similar colligative properties in water 
blends...which means it has similar boiling point elevation and freezing 
point depression.  They are very similar molecules so I doubt that a 
material compatible with EG would be bad for PG.  PG does have a slightly 
lower heat capacity too.  You also can't use the same hygrometer you do for 
EG blends.  Antifreeze testers are hygrometers that measure the density of 
the mixture and infer the glycol content.  From the glycol content they can 
calculate the freezing point depression and boiling point elevation.  So, 
they are marked in degrees, but if the density is different (which it is for 
PG) the calibration (scale) will be off.

Propylene Glycol is not toxic.  It is a common food additive...it gives root 
beer the foamy bubbles vs. cokes big fizzy bubbles.  It is also a mild 
preservative.  But...the additives may or may not be toxic...not to mention 
what happens to them after a couple years in the car.  The PG used in Sierra 
is not food grade either...that means it could contain arsenic, low levels 
of EG and other goodies found in the petroleum based propylene from which 
it is made.

If you are worried about pets or kids getting into coolant...best advice is 
to keep them the hell away from the garage if they're dumb enough to go 
drinking the fluids found there.  Except for the condensate dripping from 
the AC evaporator, I wouldn't consider anything in a car to be non-toxic.

 - Mitch