There are two main purposes of additives to straight water for cooling purposes. Anti corrosion, which seems far more important when aluminium is used in engine and radiator components and not just cast iron copper and brass. Then there is anti freeze. Am not sure if compounds other than ethylene glycol are commonly added to water. However, it has lower specific heat than water and reduces efficiency for transferring heat. Also, I gather it tends to leave a film of low conductivity on surfaces inside block and radiator which also reduce cooling efficiency. Seems that even in snow country in Australia where temperatures never get anywhere near as low as common winter ones in many parts of eg North America and Europe, nowhere near as much anti freeze is needed - if at all. eg Apparently 33% ethylene glycol solution protects down to minus 18 degrees Celsius. Also, seems if you don't need anti freeze, best to not use it at all. For several years. I have just used (green) Alfloc 3677 solution which is a corrosion inhibitor but not anti freeze.
