Suitable coolant / Corrosion inhibitor.

[Lang]

You need to remember with Glycol (and many other additives) the cooling efficiency is greatly reduced over plain water and the increased boiling point is required. There is a considerable difference in temperature in an engine running additives and one running plain water under the same conditions.

Modern engines like a bit more heat to run efficiently but the old ones like their 180 degrees. So we now have high pressure radiator caps and high boiling point additives including the anti-corrosion ones necessary in alloy engines particularly.

Lang