Sid, re the wear v temp graph. Was that taken from a study which altered the oil composition to match the expected running temps ? The main reason cars get wear at lower cylinder temps is the oil is not flowing properly providing the optimal boundary layer for friction reduction because the oil is specified for optimal running temp.
eg the RX-8 has an oil thermostat to control the oil flow and ensure it gets up to temp as quickly as possible.
Cooling fan temps between cars can be confusing too as without knowing the measurement point and the coolant flow around the critical cylinder and head it's impossible to say what temp things are really at and why.
But yes, engine management maps pay close attention to coolant temp as a warning of too much retardation though I suspect now much less so with sophisticated anti-knocking sound sensors and post combustion gas analysis.
"A woman without curves is like a road without bends, you might get to your destination quicker but the ride is boring as hell'