Drawing a conclusion as to the degree of hydrotreating (if any) of the base lube stock contained in motor oil could be an exercise in futility. CAS#s, when MSDSs are available, only tell whether the base oil is petroleum, PAO, or whatever. Within the CAS#s begining with, "64" we only know they're petroleum. The exact same full CAS# beginning with "64" could be anything from Group I to Group III, and I don't remember ever having seen a case where an oil company bothered to explicitly define the base oil grouping in an MSDS*. Further complicating the issue is the fact that ExxonMobil is not only the world's largest refiner of base lube stocks and finished oils (their site blather), the company also has been one of the few technology companies at the forefront of hydrotreatment R&D and will sell a complete turnkey operation or convert an existing refinery to produce Group II and Group III base lube stocks by competitors - for a price of course... (The company might have "lost" their arbitration case against Castrol regarding the use of the term "synthetic", but the company's been crying all the way to the bank ever since!) If I were a betting man (and I'm not...), my best guess would be that ExxonMobil conventional motor oils are just as apt to contain Group II base lube stocks as any of the other majors regarded as using the same. For one thing product data sheets for DC and Superflow oils show flash point numbers equivalent to or superior to ExxonMobil's competitors'. (It may be possible to achieve a high flash point through additives, but it may actually be more economical to do so by just starting with a superior base oil to begin with...)
*Older labels on Havoline conventional motor oil bottles plainly stated on the back that the oil was "formulated with high quality, Group II base oils". The newest Havoline "Old Timey" racing car labels are no longer that specific, though that's no indication they've regressed to Group I stocks either.
