Why is antifreeze supposed to be diluted 50/50?

[John R. Burgoyne]

I have heard various explanations of why antifreeze is supposed to be
diluted 50/50. My question is, why not just use 100% antifreeze?

BTW, how accurate are the stated coolant system capacities?

Robert

[Walter A. Koziarz]

In article <1991Jan1.0...@eng.umd.edu> burg...@eng.umd.edu (John R. Burgoyne) writes:
>I have heard various explanations of why antifreeze is supposed to be
>diluted 50/50. My question is, why not just use 100% antifreeze?
>

excerpted without permission from _1990 Service Manual, Rear Wheel Drive Truck,
D&W 150-350, Ramcharger_ copyright 1989 Chrysler Motors
for educational purposes only --

Group 7, pp 11,12:

Pure water -- for purposes of heat transfer only, water is able to absorb more
heat than a mixture of water and ethylene glycol. But water freezes at higher
temperatures and allows corrosion.

100% ethylene glycol -- the corrosion inhibiting additives in ethylene glycol
need the presence of water to dissolve, without water, they form deposits in
the system which act as insulation causing the temperature to rise as high as
300F... In adition, 100 percent ethylene-glycol freezes at -8F.

The antifreeze concetration MUST ALWAYS be a minimum of 44 percent, year-round,
in all climates... Where required, a 56% ethylene-glycol, 44% water mixture
will provide a freeze-point of -50F

CAUTION: RICHER MIXTURES CAN NOT BE MEASURED WITH NORMAL FIELD EQUIPMENT and
can cause problems associated with 100% ethylene-glycol.

end of excerpt

>BTW, how accurate are the stated coolant system capacities?
>

Not sure.... probably +/- 5%???

>Robert

Walt K.

[Peter DUNIHO]

In article <1991Jan1.0...@eng.umd.edu> burg...@eng.umd.edu (John R. Burgoyne) writes:

Because it is the property of the mixture, not of the actual anti-freeze,
that lowers the freezing point. That is, anti-freeze and water individually
will both freeze at a higher point than the two mixed. That, and also
I seem to remember reading something about the heat transfer capabilities
of anti-freeze being worse than water, so that the cooling system would not
work as effectively on 100% anti-freeze.

Pete

[Lon Stowell]

The boiling point of the proper mixture is higher as well...and
most modern cars stress the boiling point considerably by
pressurizing the cooling system.

The only real accurate way of getting the right mix is by
checking the specific gravity...a verrrrrry complex procedure...

Luckily, small errors either way have minor effects...