This SAE Recommended Practice applies to refrigerant blends (multicomponent refrigerants) intended for use as retrofit refrigerants to replace CFC-12 (R-12) in mobile air-conditioning (A/C) systems. Since the composition of non-azeotropic refrigerant mixtures changes as refrigerant is lost, either through the vapor phase or the liquid phase, the method of charging A/C systems is important. The purpose of this document is to determine the proper refrigerant phase, liquid or vapor, for system charging by relating system performance changes t the charging method. This document is complete only when combined with the requirements of SAE J1657.