Propylene glycol is, because of its favorable toxicological properties, used as a base material for automotive engine coolant formulations in a number of European countries. In the present paper propylene glycol and ethylene glycol are compared with respect to relevant engine coolant properties like heat transfer characteristics, freezing protection, cavitation and erosion-corrosion, rubber compatibility, and toxicological properties. These properties are largely determined by the chemical and physical properties of the coolant base material rather than by the additive package which controls mainly corrosion inhibition.

Propylene glycol offers distinct advantages over ethylene glycol as a coolant base fluid as regards its toxicological and environmental properties and its cavitation resistance. With respect to the other properties both types of glycols behave very similarly.