Well, in the final analysis, I am not convinced that what group base oil is has all that much to do with how long an engine will last. I have taken a couple of Cummins diesels to well over 1 million miles, one of them to 1.4 million, without major repairs, on a conventional Group II Kendall 15w40. My dad took a 1974 Pontiac Catalina to over 250,000 miles on a conventional straight 30w, year round. I run my diesels across the upper tier of the U.S., Ontario and Quebec, year round, on a 15w40 Schaeffer syn blend (25% PAO 75% Group II+) and get fantastic oil sample results doing 25,000 mile / 500 hr oil changes, and no engine related down time except for normal maintenance like valve adjustments and such. No reason to expect that the engines will not give me the same 1 million plus miles before any issues.
Now, all that being said, it is going to be a tough sell to convince me that a boutique PAO oil that costs twice as much or more is going to do a whole lot better. I have seen engines on synthetics that had issues on an equal level with those on conventional base oils. The add pack has as much or more to do with things as the base oil. PAO base oil is great, but it is not the savior of the world. It has it's limitations also. And irregardless of the marketing behind it to convince folks that it is the cure for all our ills, how folks maintain and operate their engines has more to do with longevity than anything else.
Just pick up on a quality motor oil at meets the specs your engine needs, at the best cost you can. No reason to overthink the issue. Group III, Group IV, GTL, who cares. They will all exceed anything your engine needs.
