Chasing this cooling issue for months

But, what the gauge says isn't what concernes me.
It's what the overcooling causes that does.
I know for fact that it is running too cool on the hiway.
I have a thermostatic control on my cooling fan that coinsides with the gauge reading, so if I set the thermostat under the hood for the fan to come on at 210, it comes on when the gauge inside says 210 so I know that it is giving me a correct readout.

Like I asked and it always seems to come back to, Why is 175 degree coolant passing through a 195 stat?

The only thing I can think of is that the coolant flow/pressue is forcing it's way past the stat when the stat reaches 175.
This is the only reason I can think of.

RedFish said

I know very little about aftermarket gauges. does your temp gauge have a nitrogen filled copper tube and bulb that supplies the signal ? If so , is that tube insulated ?
i'm just imagining a tube routed high under the hood and/or passing through a oversized hole in the firewall. Ambient air flow at highway speeds could lower the nitrogen signal to the gauge.

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