PAG vs Ester A/C Lubricants

What are the differences between PAG and Ester A/C lubricants. Are they
interchangable? Why or why not?

 

Just about everything. Lubricity, refrigerant miscibility, compatibility
with mineral oil and chloride residue, hygroscopic properties...

Not really, no. There is overlap in their applicability, but it's best to
use the type of lubricant specifically called for by the system under
repair. What are you trying to do?

DS

 

In general, when the system calls for PAG, I use PAG. On older systems that
started with mineral oil and R-12, I generally flush as much oil out as
possible and use ester oil since it is supposed to be "compatible" with
mineral oil and 134A. There was a rather detailed article in one of the
trade rags a few months ago (might have been Motor Magazine) that detailed
all the differences. Maybe you can find that article online somewhere.

Cheers,

C

 

PAG is a better lubricant than Ester (although not as good as mineral
oil, but mineral oil doesn't work with R-134a.). Plain PAG, however, is
highly reactive in the presence of chlorine (residue from R-12) and will
turn into brown goo. There are stabilized PAG oils on the market
("double-end-capped" PAG) that are supposed to be stable in the presence
of chlorine, but I question just how stable they are in the long run.
Will they start breaking down after 3 years? 5 years?. PAG oil also
absorbs water as readily as brake fluid, and shouldn't be used if stored
in an opened container for any length of time. Buy only enough for your
immediate needs.

Ester (aka POE) is less reactive and in fact can be used in straight
R-12 systems. But of the 3 available oils (PAG, POE, and mineral) it is
the poorest lubricant. But, since mediocre oil is better than oil that
has been turned to brown goo by chlorine, POE is usually used in R-12
retrofits. It absorbs water also, but to a lesser degree than PAG.

 

And then there are these newer oils showing up:

http://www.thetoolwarehouse.net/shop/CLP-51105.html
http://www.rocoil.com (server's down as of 3PM EDT 7/22, but I pulled it
up the other day after learning this is what's in my '89 Ram's system)

DS