Thanks for the input - you are right that all the blends do have different 
fittings and must be kept separate when recovering - so shops won't want to 
use several. My shop was looking for a different one to try, and since I'd 
cover their cost for initial tryout (which didn't need the recovery gear) - 
this was a good chance for them to check out FR12.

The blends are all filled by liquid weight - the included spec sheets say to 
use 90% of R12 weight for FR12. Although the frigc web site doesn't mention 
it, FR12 is now available in 12 oz cans - so it is possible to install with 
the low-cost piercing rig instead of setting up for the 30lb cylinders and 
scales - that's what this shop did for a first try. The instructions also tell 
how to use temp & pressure gauges to "top up" a system when you can't 
completely discharge and fill fresh by weight.

Among other national chains many Jiffy Lube shops are starting to use FR12 - 
so service while travelling should be possible.

I suspect many of their problems after converting cars to R134a were marginal 
components which might have failed soon anyway - just the added stress of the 
higher discharge made them fail faster. So if your system is in good shape 
R134a can be a good decision - it is the most available when you need service.

I was most concerned about my '87 camper - as it's A/C is most marginal in 
trying to get cool air to the front. The non-campers distribute the cool air 
much better and "top" efficiency isn't as critical.

Tom Brunson
'87 Westy 160K
'91 Carat 103K
etc

>As a fellow Hot Country Texan, I had to chime in on this one. My auto
>A/C man is a personal friend of 25 years, not a German shop. In my quest
>for R-12 replacement he showed me the list of all substitutes including
>FR-12 and he told me all apparently work well. But the downside is that
>nearly all of them require guages or special equipment that the standard
>auto A/C shop will not have. jThis would mainly be the recovery
>equipment they have. In the servicing of your unit, with thier recovery
>unit they are not allowed by law to co-mingle any of the diff
>substitutes in their recovery equpipment. 
>All refrigerants -must- be recovered if a system is being worked on. And
>theoretically (legally) they must have a separate recovery unit for each
>refrigerant they service. Secondarily, they all wiegh in at different
>wieghts, and the shop must have a different unit for wieghing the
>refrigerant when they put it back in (in case the system is low and they
>have to add some.)
>My friends shop has settled on only converting to RF-134a and are
>apparently having very good success. This forced them to only purchase
>one additional set of "tools" to maintain these systems. What they have
>learned (not sure where) is that the RF-134a does indeed run at a higher
>pressure that R-12 and they were instructed to fill the system w/20%
>less (by volume or wieght: I'm not sure which) and that this releives
>the pressure on the system (compressor) and cools almost exactly as well
>as R-12.
>There's what I've heard. My system is still R-12 until I need a bunch,
>then I will go RF-134a for the above detailed reasons.
>My nickels worth.
>Mark B. Magee
>87GL 83K
>Kemah TX USA