In short, this answer has 2 parts. If your car was made in the US in 2021 or later then the manufacturer was required by the EPA to use R1234YF in an AC system. General Motors was the first U.S. manufacturer to use R-1234yf refrigerant in the 2013 Cadillac XTS. Since then, many manufacturers have begun using the refrigerant in their new vehicles. So to determine if your car uses R1234YF then your best bet is to consult your car’s manual, look under your hood for manufacturer tags with AC refrigerant information (all vehicles have them) or just conduct a web search like this: “refrigerant for (your vehicle’s year) (your vehicle’s make) (your vehicle’s model)”. Here is an example: “refrigerant for 2005 honda accord”.