Increasing use of propylene glycol (PG) in engine coolant applications raises technical issues related to antifreeze recycling. This paper reports the results of experiments which demonstrate that propylene glycol is compatible with present-technology systems. Examples of the performance of two widely approved antifreeze purification techniques on waste coolant containing propylene glycol are provided. In addition, results on reinhibition of the effluents from these two processes are reviewed. Finally, a simple method for compositional and freezing point determinations of commingled (ethylene glycol (EG) and PG)/water mixtures is described.