R12 is heavier than air man, it is all a farce, it does not harm the ozone 134 is much more dangerous.
Dupont had some incentives to rid the world of R12.
a short read below. I have thought about sticking some 12 in my newer car my 134 system see how she works then.
http://avidinvestments.com/Freon.html
Umm, it would probably work, but not very well, different orifice.
So what about that nitrogen in tires ....good idea or ...8/