----- Original Message -----
From: Andrew B. Lundgren <lundgren@byu.net>
To: <mgs@autox.team.net>
Sent: January 27, 2001 9:15 PM
Subject: [Fwd: Good Coolant Discussion from an delphi expert
opinon. LONG little LBC]
> I picked this up on another car list I am on. I found it
interesting.
>
> -------- Original Message --------
> To: miatapower@milewski.org (Miata Turbo/Supercharger list)
>
> >> 'Jim Crider wrote'>>
> "Here's a response from someone who designs vehicle cooling
systems for a
> living (that would be me):
> Strictly looking at the heat transfer coefficient, straight
water is the
> way to go. HOWEVER... straight water has its problems, notably
a lack of
> certain additives that prevent cavitation of the water pump at
high speeds,
> corrosion of the various metal bits present in all engine
cooling systems,
> surfactants to lower the surface tension of the coolant
(allowing it to
> "wet" the surfaces of the coolant passages better) and
anti-foaming agents
> to keep the surfactants from making big bubbles.
>
> All these are present in antifreeze/coolant. The surfactants
and
> anti-foaming agents are present in Redline Water Wetter.
>
> Water Wetter has limited to no benefit in a system using a
commercial
> coolant -- it's simply adding more of something already present
in
> sufficient quantity.
>
> Another drawback to straight water is that the freeze point and
boiling
> points are closer together than a mix of coolant and water. A
50/50 mix of
> ethylene glycol and water will boil at 220F at atmospheric
pressure at sea
> level, compare with 212F for straight water. A pressure cap, by
the way,
> adds about 3 degrees F to the boiling point per psi above
atmospheric
> pressure. And of course, water freezes at 32F, while a 50/50
EG/W mix will
> freeze at about -35F. This of course is useful should you live
somewhere
> that gets cold (that would be most of the country this winter,
it seems).
>
> There are two types of base coolant stock available right now:
Ethylene
> glycol (EG) and propylene glycol (PG). Currently, no engine
manufacturers
> selling product in the US recommend PG (sold by Arco as Sierra
brand
> coolant), most caution against it (check your owner's guide).
PG has a
> higher boiling point than EG (straight), but has a lower
heat-transfer
> coefficient. EG coolants also come in several flavors,
depending on the
> additive package (more below).
>
> BTW, PG isn't truly non-toxic. It's LESS toxic than EG, but PG
coolant
> contains various and sundry additives that aren't really good
for you. The
> LD50 (lethal dose in 50% of ingestion cases) for PG is about 4
times less
> than EG's LD50, but that's means we're talking along the lines
of 16 ounces
> instead of 4 ounces for a small kid or large dog. And once it's
been in a
> cooling system, it's picked up contaminants (metals, etc.) that
aren't
> terribly good for you. Arco got in a fair bit of trouble and
had to
> re-label Sierra (including all the stuff already on store
shelves) a few
> years back when the FTC challenged their advertising claims and
found them
> lacking in accuracy. Basically, the less-toxic claim only
applies if you
> pour the stuff straight out of the bottle and onto the ground.
Don't
> bother with it. And treat *any* used coolant as low-level
hazmat. Small
> amounts can be disposed of in sanitary sewer systems, but you're
better off
> making nice with the operator of the neighborhood quickie lube
place, who
> will be able to take it off your hands and get it into the
recycling
> stream, sometimes for a nominal fee. You're already talking to
him about
> your used motor oil anyway, right?
>
> The green-dyed EG "conventional" coolant we all know and love
has an
> additive package based around a silicate (and sometimes also
phosphate)
> based anti-corrosion additive. It's well-established and does a
good job.
> It can go 5 years/50K miles without worry.
>
> A few years ago, someone thought a long-life coolant (original
plan: life
> of vehicle) would be a Good Thing. This lead to Organic Acid
Technology
> coolant (OAT), which is marketed as "DexCool" by GM and has been
> factory-fill in their products (except C4 Corvette -- not sure
about C5
> Corvette) since 1995. It's the orange or orangy-red stuff.
Someone along
> the line decided the word "acid" was a Bad Thing to try to sell,
so OAT was
> recursively changed to Organic Additive Technology. It can go 5
years/100K
> or 150K miles -- provided it's not mixed with other coolant.
OAT has less
> cavitation resistance than silicate-based coolant, and can
attack certain
> sealing materials, so it's not a good idea to convert a
green-coolant car
> over to OAT unless the manufacturer says it's okay. OAT also
has a
> tendency to stain translucent plastics in things like overflow
bottles and
> pressurized de-gas bottles with a funky brown crud. Oh, and OAT
from one
> manufacturer isn't necessarily compatible with OAT from a
different
> manufacturer. Texaco is GM's OEM supplier and is licensed to
use GM's
> "DexCool" trademark on their aftermarket packaging. I'm not
aware of any
> other company being licensed to do so.
>
> Many European automakers use a hybrid of OAT -- HOAT (Hybrid
Organic
> Additive Technology -- clever, huh?), which is the OAT package
with a small
> amount of silicates added to increase the cavitation resistance
and make it
> less aggressive against those seals and gaskets. This is often
pale yellow
> in color. DaimlerChrysler is using it in several car lines now,
too,
> notably the LH sedans and the new minivans (It's possible the
> Sebring/Stratus twins now use it -- I don't have that handy at
the
> present). This stuff seems to offer pretty much the best of
both worlds --
> it's not quite as long-lived as straight OAT, but it is much
better behaved
> in operation than OAT, much like conventional coolant.
>
> Note that these three different additive packages are not really
> cross-compatible. No, they won't eat the insides of your
radiator if you
> mix a little of one in with another in a pinch, but you'll be
better to get
> the system flushed out and a fresh mix of 50/50 whatever your
car needs put
> back into it.
>
> In my own cars, I run a 50/50 EG/W coolant mix. I happen to own
cars that
> take conventional coolant, but if I owned a car that came with
OAT or HOAT
> from the factory, I'd likely stay with it. The anti-corrosion
additives,
> in particular, leave residues on the walls of the various
coolant passages
> (that's how they work -- the residues coat the base metal and
prevent
> corrosion), and it's tricky to convert an engine that's been run
with one
> style of package to use another package and get the full
benefit.
> Switching from conventional to OAT, for instance, requires a
mild acid
> flush of the cooling system after removal of the conventional
coolant and
> before pouring in the OAT if the long-life corrosion benefits of
the OAT
> coolant is to be realized. Just pouring the OAT in after
draining the
> conventional won't gain the full measure of added coolant life
the OAT
> marketers (notably Texaco) like to use as selling points.
>
> Radiator caps are a whole topic unto themselves. Ask me about
them another
> time -- my lunch hour is over and I gotta get back to work. :)
>
> Hope this is helpful.
>
> Jim Crider"
> An address at delphi.com
>
>
> CB
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