Ted wrote:
> Speaking of antifreeze. Quick question for these sleeved engines and
>cooling...
>
> My local mechanic recommends running pure antifreeze in any and all
> cars. Not only does he believes running 50/50 is a gimmick that leads
> to a need to more quickly change coolant, but he believes it causes so
> harm to the engine.
>
> As we near winter thaw, is it best to put pure antifreeze in these
> engines, or just water??
>
> Thanks for your chemical and mechanical expertise!
Does he get a commission on selling antifreeze?
Chemically, it won't cause harm to the engine--but it does increase
the chance of overheating. The ability of ethylene glycol to
transfer heat is not as good as water, and has a poorer specific
heat. This leads to more nucleate boiling in hot spots, which can
accelerate the rate of overheating, encouraging boilover and coolant
loss, in large part due to the specific heat of ethylene glycol
(.57) or propylene glycol (.59), compared to water (1.00), specific
heat being the amount of heat required to raise the temperature of
the substance one degree F. (One BTU is the amount of heat required
to raise one pound of water one degree F.)
The lower the specific heat, the easier to raise the temperature of
the coolant and the less heat transferred per unit volume of coolant.
As for the need to change coolant more frequently, most newer
antifreeze formulations have more corrosion inhibitors than in the
past (in part because aluminum heads are now commonplace) and can go
for longer periods without changing (the antifreeze itself breaks
down very, very slowly--it's the corrosion inhibitors that are
expended). Antifreeze should be changed, therefore, because of the
neutralization of the corrosion inhibitors--so, if 100% antifreeze
would have to be changed every four years, 50/50 gets changed every
two years. No net cost savings.
If it never froze anywhere, there would be no need for
antifreeze--just corrosion inhibitors. This is pretty much what most
racers use (along with perhaps surfactants such as Water Wetter to
improve coolant contact with surfaces, and, therefore, heat transfer).
In short, your mechanic is wrong.
Cheers.
--
Michael D. Porter
Roswell, NM
Never let anyone drive you crazy when you know it's within walking
distance.
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