As 12many says, a fallacy.
And a bit of common sense shows this.....
The cooling system is a closed cct. If you leave the coolant in the rad longer, then that means the coolant is in the engine longer...picking up even more heat. When it arrives at the rad, the coolant is now hotter & the rad has more heat to dissipate.
Sometimes, trying to lower the temp of a hot running engine requires a systems approach. It may be that no one 'thing' on it's own is going to reduce temps by 15*.
But if you make 5 improvements that each knock off 3*, then you have your 15*.
Improvements can be sometimes obvious, others not so obvious. Obvious would be more efficient water pump, better fan, running pump faster.
Less obvious would be making sure the gaps around the shroud are sealed to the rad core so that all the air is pulled through the core. Less obvious are things like mating parts. Where coolant exits the heads to enter the intake [ some engines ], make sure the holes line up. Some Edel manifolds I have seen have smaller holes in the intake causing a mismatch. Result is turbulence & reduced flow.
