There is lots of confusing and conflicting info out there about how to handle cars with R12 refrigerant. At $50-60/lb, R12 is no longer an economically viable option for those of us with older cars. Conversion to R134 can require changing a lot of parts including compressor, drier, expansion valve, and pressure switch. This hardware amounts to about $400 on a DIY basis. This does not include flushing the condensor and evaporator and recharging. Maybe another $200 if done by a shop.

Then there's Hot Shot which you can buy at Kragen and the like. But it contains R22 which contains many bad things for your system. Or you can try Enviro-Safe ES-12A. This stuff appears harmless expect it contains flammable ingredients and thus has not been approved by the EPA. (Worried about possible fire or explosion, particularly in an accident.) But you can buy Enviro-Safe without an EPA certificate. Then there's Freezone (RB276) which appears to be perfect but requires an EPA certificate and is only available in 25# (about $220) containers. (An EPA certificate can be gotten for $20 and some testing hassle via the internet but not really a big deal.)

Although against EPA regulations, both RB276 and ES-12A are compatible with R12 and thus could be added without purging the system. I am told many mechanics do it. But the EPA says you can't mix refrigerants.

My preference would be to go with the RB276 if I could find someone who would sell and/or install it in a small quantity.
My second preference would be to use the ES-12A which costs about $50 for enough for probably 2 chargings plus an adapter hose. That would beat spending $100 plus a year for the R12. I haven't heard about many cars blowing up using the stuff!

As far as the EPA is concerned, their heart may be in the right place, but after the MTBE gas additive fiasco I personally think you do your own research and go from there.

Any comments from those using RB276 Freezone or Enviro-SAfe AS-12A or anything else would be appreciated.

1980 240D
252500 miles
Other than the A/C, a cream puff.