Hi,
Black_35TH - This subject has been discussed before
Mobil Chemical is the World's only Manufacturer of of very low and very high viscosity PAOs and they sell them to a wide range of Blenders (Oil Companies) for use as base fluids in engine and other lubricants
Spectra Syn, Spectra Syn Plus and Spectra Syn Ultra are but three product definitions along with PureSyn and SuperSyn and others. Esterex (esters) and Synesstic (ANs) are other Mobil components used in lubricants. They come in a wide range of VIs and viscosities
Tri-Synthetic branding is still used on some M1 packaging in Europe
SuperSyn is used by some Blenders (Oil Companies) in their own product descriptions
It is no doubt a Commercial reality that EM wil retain the best products for their own (and possibly exclusive) use
These chemical base fluids no doubt add much to their range of Mobil lubricants from Group 3 and beyond - and not only those sold as Mobil or Delvac products either
IMHO we should not get hung up on lubricant Groups - with today's complex lubricants it is all about end user and product performance