Coolant and HP

[Vimes]

The backstory - my beater truck has been having HVAC problems, which I finally tracked down to a micro-leak in the evaporator. Out came the dash, and while I was in there I replaced the heater core. I also replace the thermostat and all hoses because why not? The truck came with some sort of red coolant, and I replaced it with the yellow coolant I normally use in everything.

Now, for the odd bit - keep in mind that I was only replacing the evaporator, so basic repairs and not performance upgrades but blow me down if the SOTP dyno didn't register a noticeable power improvement. The red coolant (which I've actually never used before) didn't look dirty or worn, and I didn't see any corrosion, and the old hoses and thermostat actually looked like they were in good service, but it got me to thinking. How much of a difference does coolant make on HP production? The perceived power increase was not anything I was expecting at all.



A quick web search didn't show anything, but has anyone ever heard of dyno testing of different coolants? It might be worthwhile for someone who has a dyno and a lot of spare time and cash to look into considering how much of a difference it takes to register a difference on the 'ol butt dyno. Obviously coolant won't create HP, but I can see lubricity and resistance to flow affecting the amount of HP needed to move coolant through an engine.