Way back when,
I used the syntec in my F150, that was before I knew better. As I can't see paying $$$$ for a conventional oil as compared to a syntnetic that is far superior in oxidation, stability, and cold weather performance.
Now there is some good points to a Group III oil. From what I understand, they work better with some addtives, also they are less expensive to process than a Group IV/V oil. Therefore the price should be reflected accordingly.
For instance if you could get a top quality Group III designed for extended drains of 10,000+ for say $2.95/qt. That would be good value and performance for a passenger car/diesel truck.
I wouldn't use if for a high performance engine, that is raced or turns high temps(like a turbo, or supercharged engine) I feel that it is more suseptable to cokeing.
Anyhow, I would like to see a decent blend of Group III/IV/V at an attractive price. As long as they promised that they use no less than a Group III!!!!
Back to the syntec, I have seen some decent analysis on the 5w40 that was run 10,000 miles in a VW Jetta. As this is what is recommended in the Owners Manual, both the oil and the drain interval.
You can do a search for it on the tdiclub site.