[V8] coolant

[d saad]

That is an excellent question - and I don't have a good answer.
I
spent a lot of time researching this yesterday, and it really seems that
the German formulations are tuned for water conditions there. The Zerex
stuff is tuned for water conditions here. Further more, all the reading I
did says some amount of phosphate is a good thing (provides protection
after very destructive cavitation bubbles pop), also some silicate
(provides waterpump seal protection and metal coating), yet the German
brands remove it all. There seems to be a lot of science going into this
stuff, and some competing ideas - like the dex-cool "OAT
based"
and now HOAT.  The Japanese also have a different
take. They seem to stay away from the OAT stuff, preferring a short change
interval.
As for the factory knowing best, it seems VAG went from G11
to G48 to G12 - only to have the same problems GM did so they went to
G12+. It seems they are guessing too.

G48 (which I believe is
blue and what you get currently at a VAG dealer if you ask for G11), is
also spec'd by BMW, and is direct cross to Zerex G-05.
Mercedes also
directly specs the Zerex G-05, and both these companies use the same
materials as Audi.

Confused yet? I am.

My motivation
is not so much cost but availability btw, and I don't want another water
pump or head gasket failure.

Dave

> Just like the
recent oils thread, why would you use something other than
> what
Audi specified for its cooling systems?  I purchase Autobahn brand
> phosphate-free blue coolant from the dealer.  It costs half again
as much
> as the standard green crap from FLAPS.  Not much of an
additional expense
> (considering the cost of fuel today) for
something you use a gallon or so
> of every two-three years.  I
buy several gallons at a time (five operable
> Audis in the yard)
and always carry some in each trunk.  It is completely
>
compatible with the green stuff in an emergency.
> 
> d
saad <dsaad at icehouse.net> wrote:
> 
> I was using
Zerex 5-year orange coolant. I think it is similar to
>
"dex-cool".
> The inside of my motor looks fine - no
scale or
> buildup or corrosion, and the radiator is also still
good, and not plugged
> up at 150K miles. However, I began to
wonder why the head gasket failed
> the way it did.
> 
>