There is an interesting article in this months "NAPA News", compliments of
your (my?) NAPA store.

In the article, the author contrasts the "green" and the "orange" coolants.

Bottom line:  the 2 coolants, although they are 94% the same (ethylene
glycol base) they different significantly in the formulation of the additive
packages.  Each additive package has its own "strategy" for corrosion
control.

The green coolant uses silicates and phosphates to for a corrosion
inhibiting coating inside your cooling system.

The orange coolants uses organic acids to develop a similar (but different)
coating to protect everything.

The article goes on to mention some technical points, but is clear on one
(actually two) points.  1.)  Once you start a system with one or the other,
changing to from the green to the orange (or visa-versa) the second chemical
installed in the system cannot propagate the coating throughout the system.
Since, by replacing the first by the second, the first is no longer coating
and re-coating the system....bottom line:  replacing orange with green and
visa-versa leads to inferior protection, maybe even worse then the original
coolant.

The article goes on to discuss the electrical potential in the cooling
system, which calls back to mind the simple test of hooking a voltmeter to
ground and the coolant (actually sticking the probe in the coolant) and
verifying the potential around (something like) 1.2 volts or less.  Greater
then 1.2 volts indicates something is being corroded as a result of the
different metals (battery effect) inside the engine.  Coolant interferes
with this corrosion, and the lower the voltage, the better.  Change the
coolant to lower the volts; part of the potential is caused by the dissolved
cooling system bits that the coolant is buffering - as the volts go up, the
coolant is buffering more and loosing corrosion prevention capability.

The article continues into a coolant recycling thread, which was of interest
to me, since I built a coolant recycling column for my Cal Poly SLO senior
project back in 1989 or so, but not too much interest to folks outside the
shop environment where coolant is being recycled.

So:  don't change from green to orange; use distilled water, and keep the
volts in the cooling system low.

Words to live by, no?  See the whole text at your local NAPA dealer.

Roger Bowman - bowmanrp@ earthlink.net
Live Smart.  Think for Yourself.  Transform the Future