What is the purpose of a thermostat?

[Dave Samson]

I've followed this thread with great interest having suffered overheating problems for a long time. I never did get to the root of the problem although by elimination I suspect that the cause was residual air somewhere in the block which I was unable to flush out.
My solution was rather drastic in the end, I eliminated the mechanical water pump and thermostat, replaced them with a staged motor electric pump whose pump rate is controlled by the voltage it receives which is determined by the dial setting on the control unit which gets its water temperature from a probe in the top radiator hose.
The bottom line is that I can dial in the temperature that I want it to begin pumping at 3V. then in temp. increments the pumping rate increases by additional voltage to 6V then 9V then 12+V for different situations depending on how I want the engine to perform.
No more overheating problems, no air locks.

But I don't think that this overheating problem should be seen in isolation. I would also be concerned about the engine oil temperature, a figure that is far more important than water temperature.

What oil temp. readings do you get when the water temp is 210F at standstill ? How do the oil temperatures move around relative to the water temp. ?