> You can actually hear my '96 motor quiet down as the oil makes it's way through the head. Takes about 15 seconds. I wait for the engine coolant temp to reach 75c before I give it a good wick. It fluctuates between 75c and 85c under good load.

Pretty typical of engines of that vintage with hydraulic lifters.

> Interesting to me, is that when idling down a hill it does not drop, but if left in gear going down a hill it does drop in temp. It can actually get itself below operating temperature in gear going down a hill. I presume because the heat being pulled out via pumping air through the combustion chamber is greater than the thermostat would allow to be pulled out via the radiator.

I didn't think that would significant but I could be wrong. Is it a diesel or gasoline engine? My guess would be the thermostat is leaking or wrong temperature.

Two factors, deceleration fuel cutoff in gear not producing combustion heat, and water pump spinning faster.

I would have thought the thermostat would account for faster water flow, at least stopping the temperature drop at operating temp. But as another user pointed it, it could be a bad thermostat also.