So both are right under different scenarios?
Reading you both...
The low-temp isn't going to let more coolant through to the radiator (just sooner) but in the low speed running low thermal-loaded state the temps will be lower thus when the engine needs more cooling the radiator coolant starts out from a lower base.
Raise the temps toward or to the thermal max of the radiator (as in racing or A/C on on a hot day) and the low-temp thermostat will have no effect as the same coolant flow will get to the radiator and the radiator will cool to its max (if the leaves have been cleaned out).
It will take a while for the coolant to return to lower temps (because that only happens when the radiator can remove more heat than the engine is producing) even at low thermal-load road speeds but the low-temp thermostat will allow eventual return to a lower state.
On a road car, the oil will last longer because it spends more time at a lower temp.
So I'm left with the questions:
What is the real coolant temp difference between running at a constant 40-50 MPH and 70?
Once you raise the temps to the max the radiator can handle, how long at a moderate speed does it take for the temps to drop to the point where the low-temp thermostat makes a difference?
How much does the ambient temp influence the max cooling capacity of the radiator? IOW, how hot does it have to be out on a road car (because most of ours are) before the low-temp makes no difference after warm-up?
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