Good compressor flushing method.
There really isn't much oil in Nippondenso compressors anyway. other concept to ease to process is that it is now recognised that the various oils do not interfere with each other. The concept being that the proper oil is required to be miscible in the refrigerant used. The other oil won't mix and just winds up sitting around in the corners. Just have enough of the oil required.
Jim was right though, 126 cars do decent in 134. They do have some chassis specific failures though. Poor AC is often dirty, blocked evaporators (air goes around not through enough for cooling) or a fully open recirc door will knock 10-15 degrees off duct temp.
Bosch Master, ASE Master, L1
33 years MB technician