Non-Silicate Coolants

[Robert Ducker <bducker@domain.elided>]

Thought some other Stag owners may be interested in this excerpt from a
journal (http://www.asashop.org/autoinc/autoinc.htm) for automotive
technicians concerning low-silicate coolants:

It's Time To Get Savvy On Coolants...
     Many coolant manufacturers add a silicate corrosion inhibitor to
protect aluminum components. Silicate corrosion inhibitors work by
depositing a "passivating" coating throughout the system. Unfortunately,
silicates are also somewhat abrasive. If they drop out of suspension, they
rapidly wear out water pump seals. 
     The orange-colored Dex-Cool coolant that GM started using in some 1995
cars is a non-silicate formula. After 3,000 miles, Dex-Cool has coated the
internal passages with an organic acid. This passivating coating will last
for five years or 100,000 miles. If you replace parts such as a water pump
or radiator, the coolant must recoat the new part. That's why, in normal
maintenance or repair procedures, it is not a good idea to replace Dex-Cool
with ordinary silicate coolants. In emergency situations, Dex-Cool can be
mixed with standard green coolants. However, mixing with green coolants
will reduce the life of Dex-Cool to that of ordinary coolant and you must
inform the customer of the shortened life. Why do it when you can sell the
customer on the benefits of Dex-Cool? 
     Toyota specifies its own red coolant because it is a low-silicate
formula. Honda, too, recommends its own proprietary coolant. The major
coolant manufacturers are working on low- and non-silicate formulas to
compete with these private brands. But until they are on the market, why
subject yourself to claims of improper coolant refills?

Since this article was written (1996), Prestone has introduced a Dex-Cool
compatible coolant they call Extended Life 5/150. I haven't priced it yet,
but it's probably cheaper than replacing a Stag water pump (if it works)...