[GH85Carrera]

As far as I know, all hydrocarbon (propane and such) are illegal for road use in the USA. That certainly does not stop people from using them. They are a potential firebomb in an accident. A crash hard enough to get to the engine compartment can rupture those lines and make a nice cloud of extremely flammable gas in your nice hot engine compartment.

And don't say yea, what about the gas tank. The gas tank is in a protected area inside the frame, and liquid gasoline is not that flammable. One when it is vaporized is gasoline flammable.

So a 15 MPH hit on the front end will make the crumple zone (engine compartment) crumple, and make a nice cloud of explosive. Your insurance company might want to know about that and deny coverage.

Look up the DOT and EPA regulations on hydrocarbon refrigerants. Make your own choice.

If the AC worked properly when new, more than likely is just needs a competent pro to diagnose the problem and fix it properly. It could be a clogged orifice tube, or expansion valve, or simple low on charge. Don't just dump in more refrigerant, as that can make the problem worse when working blind.

No way will I ever use propane in my car as a refrigerant. Vehicles that use propane or natural gas have those high pressure tanks in safe part of the car, and the tanks themselves are pressure tested, and have to be replaced after a number of years. AC lines are very vulnerable.