This is why I try to find out what is "probably" in oils.
Right now I'm running 12 qt V. SynPower 20W50 (PAO per MSDS) and topping off with Maxlife (blend, ~17% PAO). It's a 911 and consumes ~1qt/600 miles and has 12qt changes (total sump is ~14qt). So the SynPower almost gets 2/3rds replaced with Maxlife in 6K miles. So I 'likely' start with all GrpIV and the blend % moves toward GrpII.
In your case, I don't know the likely % or the blend or on the full synth, but it could be a GrpII, III, IV cocktail atleast from same vendor.