Originally Posted By: mesastoura
Could you please explain this?
At one end of the cooling system you have a piece of metal at a high temperature (the head)...at the other end you have the atmosphere, which is where your waste heat ends up...same for all heat engines, including power stations etc.
From air to cylinder head, you have the following as a minimumum.
Air/Aluminium passage through the aluminium aluminium/coolant coolant/cylinder head.
Every one of those interfaces takes requires a temperature difference to drive the waste heat through them, and all of the temperature differences add up.
If the coolant needs more temperature to shift the waste heat, then everything upstream of the air (heat sink) has to run hotter to push the heat along.
If the coolant has a lower specific heat (the number of degrees a liquid rises for a BTU input is the specific heat), the coolant itself has to run hotter to carry the heat out.
Best "coolant" is water in a fresh system (corrosion soon fixes that), 50:50 antifreeze is a fairly distant second, but a necessary evil.
Waterless coolants are another step in the bad direction.