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.
R134a is the most popular refrigerant to charge the AC systems inside the car.
Keep in mind that you will need to vacuum the car if the AC is discharged completely.
• You need an AC main fold gauge and a vacuum pump.
• AC Main fold gauge has three lines : blue, red and yellow. Connect yellow to vacuum pump, red to large fitting and blue to small fitting in the car.