The oil, whether it be mineral, PAG or Ester, does not circulate with the refrigerant in an RV2/R-12 system like a rotary/134a compressor system, regardless of the refrigerant you choose to use.
Any of the three oils should work on the RV2 as long as you add it to the crankcase of the compressor and NOT the charging port. THE OIL DOES NOT MIX AND CIRCULATE WITH THE REFRIGERANT with an RV2 or York/Tecumseh..
I'm by no no means an AC system expert, but according to the service manual in an RV2/R12 system the oil does mix with and is carried by the R12 through the entire system.
I think he was referring to the RV2 twin cylinder compressor used on old Mopars. The majority of the oil sits in the sump splash oiling the Compressor like a lawn mower engine does.
Yes, you are correct that oil will circulate but it will not get into the sump through the hoses. With the RV2 compressor, putting oil in the hoses is like adding adding oil to a lawn mower engine through the carburetor.
Because it will circulate, you should also add some to the system in the drier when installing everything from scratch to lubricate the other parts. i.e. compressor valves, expansion valves
I use ester oil in R12 systems because PAG and Mineral Oil are not compatible. At least the manual says they aren't so I have never tried it any other way.
