On Tue, Jun 11, 2013 at 6:52 PM, Keith Hughes <keithahughes@yahoo.com>wrote:

> R-134A doesn't cool as well in an R-12 system.  You really need a more
> efficient condenser if you want good performance.  Additionally, R-134A is
> not compatible with mineral oil used for lubricant in R-12 systems, and
> typically R-12 compressors are not compatible with POE/PAG oils used for
> R-134a from an internal seals perspective.  Also PAG and Mineral oils form
> a very funky mess, so if you're not going to flush the system first (which
> you should) use POE not PAG oil.  You must change the receiver/drier
> anytime you open the system, and especially when changing oil/refrigerant,
> if you don't want a time bomb waiting to blow (we're talking $15 here).
>  Also, expect the R-134A to leak, as the stock hoses are not barrier hoses,
> and 134A will leak out over time.
>
>
> Well, here we go, the inevitable stream of reasons that you can't do
something that everyone is already doing. I have done about six cars and I
didn't do any of this stuff and I really can't tell any difference in
actual cooling although I don't argue with the engineers who tell me that
R134 is 15% less efficient than R12.

The R134 does find leaks that R12 doesn't, but you can put in a refrigerant
with some sealing capacity if that is the case.

Jim