There are two types of glycol currently used for antifreeze production, Ethylene Glycol (EG) and Propylene Glycol (PG). The majority of antifreeze produced uses EG. EG is less expensive and provides a lower freeze point at a 50% ratio for water to glycol.

A 50/50 mixture of EG antifreeze and water provides a -34º F (-37º C)  freeze protection while a 50/50 mix of PG antifreeze and water provides a
-27º F freeze protection. EG is poisonous. For this reason, it should be assumed for health purposes that any antifreeze or waste coolant contains EG, and is, therefore, poisonous.