$40 for a can of Freon? I think /not/.

I have used Duracool in several cars for years. It works slightly better than R-12. R-134A will run at higher pressure, which isn't good for your compressor. There are several other butane mixtures. I bought a can for ~$8 at a local show. The guy said he must endure all the uneducated comments from naysayers, and some will surely chime in here. No need to flush the oil or freon, but you will need to add R-134A type adapters.

Yes, butane is flammable. R-134A is flammable and forms poisonous phosgene gas. R-134A is being replaced by butane since R-134A is a potent greenhouse gas. Home refrigerators in Europe and Japan already use butane, and will soon in the U.S. I don't see houses burning down. They put mercaptin in the mixture so you can smell a leak, plus I have never read of a car fire from using it. Pick up a 6 oz can and you will swear it is empty, so hard to imagine the threat. The EPA made fools of themselves by fighting it for years, so now they will insist on calling it something other than butane.