A New Refrigerant for Sustainable Mobile Air Conditioning Opteon YF refrigerant cools like HFC-134a in automotive air conditioning systems but has a much lower global warming potential (GWP). The difference is in the chemistry. Conventional mobile air conditioning (AC) systems use hydrofluorocarbon (HFC) refrigerants, which are composed of hydrogen, fluorine, and carbon atoms connected by single bonds. Opteon YF (R-1234yf) is a hydrofluoroolefin (HFO) refrigerant that has the same chemical elements but contains one double bond between one set of the carbon atoms. The double bond makes a big difference. HFC-134a refrigerant has a GWP of 1,300; Opteon YF has a GWP