EPA has approved below refrigerants under its SNAP (Significant New Alternatives Policy) Program as an alternative to R12 in car air conditioners other than R134A .You must buy only EPA approved refrigerant if you want to use a refrigerant blend other than R134A.
In 1990′s the most popular choice for car AC refrigerants was R12.It was manufactured by Dupont and marketed as Freon. It was chlorine based (HFC or HYDRO FLUORO CARBON) and has a very high warming potential (8500). It was banned in the 90′s because of its adverse effect on Ozone layer and search for green refrigerants started.
R134a refrigerant replaced R12 for charging Car AC’s as it was effective in cooling and has a 7 times less warming potential (1400) than R12.In recent years ,EPA has announced
• All the vehicle models starting from 2011 has to use a refrigerant with a warming potential of less than 150.
• Starting from 2017 all new vehicles sold will have to meet the low global warming potential requirement.