Vehicle Manufacturer Approval

• R134a is the only replacement for R12 use in automobile air-conditioning systems approved by all vehicle manufacturers, according to the AA1Car website.
  
  

Environmental Protection Agency

• The Environmental Protection Agency has approved a wider range of R12 substitutes for use when replacing R12. As of November 2010, these include the refrigerants under the trade names GHG, GHG-X3, GHG-12, McCool, Autofrost X3, GHG-X4, Chill-it, Hot Shot and Kar Kool.
  
  

Use

• Retrofitting R12 air conditioners with alternative refrigerants will necessitate entirely removing the R12. In addition, the EPA states that using alternative refrigerants may alter performance of the air conditioning system, and advice from a professional is advised. The EPA states that the manufacturer-approved R134a can also be the cheapest option compared to blend refrigerants on sale.