Tom I would be extremely interested to know what type of coolant each run was in your tests.
I recently flushed my Viper and filled it with Zerex G-05 since it is what my Mercedes uses (in fact it is the same color) and supposedly what my BMW uses just dyed blue. I feel those manufactures along with Toyota have the highest regard to engineering. However, I noticed the Toyota coolant formula is different than the Benz/BMW, mainly being the levels of silicates.
So how does pH levels effect performance, OAT versus HOAT formulas and low silicate HOAT versus silicate free HOAT? Would a OAT be better than the HOAT because it is phosphate and silicate free?
Some were green, some were pink, some were red...
You were typing same time I was, but bottom line is that I don't want to get into ******* contests about brands.
Everyone should know that ethylene glycol is a clear fluid. The many different colors are merely dyes. To this dyed ethylene glycol, additives are mixed in at around 6%-8%. After you make your purchase, you add 50% water and this combination is the "coolant."
The green coolants uses only silicates for metal protection. They are designed to coat the metal surface rapidly and protect against corrosion. Consequently the additive chemistry is depleted - it is all on the metal - and when it comes off again it leaves the metal unprotected. To make matters worse, the silicate "blobs" as shown in my picture above are abrasive to water pump seals.
Organic Acid Technology (OAT) is silicate free. The original DEX-COOL product is OAT. This chemistry stays in the coolant solution until corrosion is detected, then only attacks that site. Consequently, the little additive soldiers are not all used up right away and are waiting (up to 5 years/150K miles) to fight the next battle. In the mean time, the metal surface does not have a layer of "stuff" and so heat transfer is slightly better.
Some OEMs wanted a faster acting, but long-life coolant, so they developed Hybrid Organic Acid Technology (HOAT). It contains mostly OAT additives, but with a little bit of silicates. Very low levels, and from what I read, not a problem with water pump seals. When OAT was new, OEMs were undecided about what was best for their engines, so the HOAT versions (pink, orange, red, etc) came out. My personal opinion is that they are essentially all the same. In addition, the coolant manufacturers are finding that there isn't a difference in the engine appetite, so you are seeing more and more come out with a long life coolant for any engine, or that replaces any color of coolant.
(Ironically, there is consumer literature saying not to mix coolants, but think about HOAT - it is a mix of long life OAT chemistry with a pinch of silicates!)
In the end, I will say that any reputable brand long life coolant will be much more than you need. I say that because the same chemistry is used in heavy duty tractor trailers engines and those coolants go 2 or 3 times 100,000 miles with a small bottle top-up to go the next several hundred thousand miles.