Well … I hate to crash the “PAO …true synthetics” lovefest
… but …
If the Group III’s are “#@$%!.” … then what are the PAO’s? You might consider a Group III.
If not, and it has to be PAO, then I would probably go Amsoil.

Quote:
link…
The relationship between oxidation stability and antioxidant depletion in turbine oils formulated with Groups II, III and IV base stocks.
… … The results also showed a surprisingly high oxidation stability for turbine oils formulated with Group III base stock, with the oxidation resistance of the Group III systems exceeding that of the equivalent Group II and Group IV systems.
If the Group III’s are “#@$%!.” … then what are the PAO’s? You might consider a Group III.
If not, and it has to be PAO, then I would probably go Amsoil.