Larry Bible has some well-formed opinions as to why you should always seek out and use R12 to service your R12 system. And, if you live in a large market where R12 is available at competitive prices, and the climate requres you to use AC much of the time, and it needs to perform with maximum efficiency, his opinions should guide your decision on whether to convert over to 134a. That said, if your climate is fairly mild and your system is in pretty good shape and you could be satisfied with less than perfect efficiency when compared with R12 performance, then you might want to consider a conversion to 134a.

I did my old sedan two years ago using the most basic "EPA simplified method." This involved little more than removing the remaining R12 (not much, big leak) finding and fixing the leak, replacing the original dryer with a 134a compatible unit, charging with ester oil and 134a with a "conditioner," which I have no clue to what it did/does for my system. I did not flush out the old oil because I was persuaded that the two oils would not mix and the old mineral oil would simply migrate to the system low point where it would sit without causing any problems. The ester oil was billed as being OK with both mineral oil and the 134a-specific PAG oil. It's the PAG oil that apparantly is so harmful when mixed with mineral oil. That's what I was told, and so far, so good.

The results have been entirely satisfactory. My cooling is not noticably less efficient than before and I have observed no decline in cooling or other problems with any components in the system, so far. I was advised that my old hoses would leak the 134a, and other maladies were in my future. I've seen none of that. Many have cautioned that time will take its toll and I'm going to be disappointed eventually. Maybe so, but I have been happy so far. If I lived in Houston it might be different. Hundred degree heat and 98% humidity are entirely different matters and I suspect that a conversion would be far more problematic in those conditions. However, in Canada's milder summer climate I would expect the best chances for satisfactory results.

Finally, I have read that R12 is dropping in price and now competes favorably with 134a. So far I have seen no such thing, and this thread with $100-$150/pound prices would seem to bear that out. $150/pound for R12 (even $30/pound for license holders) is a far cry from $4/can for 134a at WalMart. Can anyone point me toward that cheap R12? I have a sweet 350SL that still uses it.

All that said, others will have different opinions and each should be considered with care when making a decision.

FWIW

230/8