The liquid you will need for your car's AC is refrigerant. This is a specially formulated mixture that is created to transform hot air into cold hair by absorbing and releasing heat. Refrigerant is also known as Freon, and the most common Freons are R-12, R-134A, and HFO-1234yf. R-12 was banned in the mid-1990s after it was discovered to be depleting our planet's ozone layer.