I finally got around to investigating which coolant was used originally in the M35 B(C) engine as filled upon delivery. As you notice it is a red color (actually orange per the manufactuerer's claim). I researched and found that there are significant and purposeful differences in the types of coolant / anti-freeze used. The red type that comes in the engine is a Havoline Dex-Cool Extended Life anti-freeze/coolant. It has a special additive package that is pump seal friendly. Without getting too technical or giving a chemistry lesson, it seems that the additives used are not of the silicate or other types found in many other anti-freezes that can precipitate out and be abrasive to water pump seals.
The Havoline part number is Code 7994 (the 50/50 pre-mix is code 7995). After reading the technical bulletin from Texaco. I will not blend anything with it other than distilled water and will not mix with any other anti-freeze.. I am of the opinion now that only the red should be used.
Thought this was interesting. I found the info on the internet searching for code 7994 dex-cool.
LONGHAWK #173
Red Coolant
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