What's really going to "frost my cork" on this whole M1-Grp III issue, is that I've always defended M1 against the Grp III conspiracy crackpots with the following ExxonMobil statements:
From the
ExxonMobil Chemicals FAQ's on Synthetic Base Oils
Q What is the definition of synthetic lubricants?
A Synthetic lubricants are manufactured in chemical plants by reacting components and are specifically designed to possess physical and performance characteristics that are superior to mineral oils. As a result, the molecular structure of synthetic lubricants can be precisely arranged to meet, and often exceed, manufacturers’ criteria for high-performance equipment.
Q How are Group II and Group III base stocks different from Group IV (PAO) stocks?
A Group II and Group III base stocks are enhanced mineral oils that are manufactured by a refining and extraction process which partially removes undesirable molecules that are present in the feed. In contrast, Group IV (PAO) base stocks are chemically synthesized and therefore, do not contain undesirable species.
Group II base stocks may be made by hydrotreating, hydrocracking or combinations of solvent processing and hydrogen processing. They have 80 -120 VI with more than 90% saturates and less than or equal to 0.03% sulfur. Group III base stocks are manufactured by hydrocracking and isomerizing slack wax. They generally have more than or equal to 120 VI with more than or equal to 90% saturates and less than or equal to 0.03% sulfur.
.
.
And now my comment is simply this, "Come on, XOM, put aside any synthetic fluids definition doublespeak & make a statement that Mobil 1 Regular & EP are blended from primarily PAO & AN base stocks."
Claiming "proprietary information" only grows the cloud of suspicion!