Last time I bought
R12 it was for $20/ (12/18-cant recall)oz can
R134A is about on par with that
ES-12A is about $7/can
Here is my experience
In the stock system:
R12 is the best no doubt.
R134A is merely OK, it sucks at idle because of low air movement. Its OK at speed.
ES-12A also sucks at idle, but does pretty well at speed.
I have ES-12A in my 190E. The vent temps can go into the mid 30's on an ~80F day. I'd say it does pretty well. When I first bought the car I had R12 charged into it. It leaked out in a year. I had Freeze12 put in, it too leaked out in a year (its a R134a blend after all) I put ES-12A in and it didnt leak out at all. Yes there is probably a leak but at the time I was not spending the time/money to deal with it.
I have Es-12A in the one 300SD. All stock system with R4 compressor. At idle speed it is useless. At 40mph+ its comfortable. I suspect you'd be OK in the New England area with it and for <$10 a can..why not ?
IMO, the PROPER way to go is to convert to a nicer Sanden compressor and use a larger condenser and larger fan assembly AND to clean out the evaporator but that is oodles of work and money.
The 420SEL has a R12 system. Its probably the coldest vehicle aside, but I suspect it has a leak as well somewhere.
