The hydro crack process is a synthetic process.
In general, that is true. However, hydrocracking can produce either Group II or Group III base stocks. Larry, your favorite Delo 400 15W-40 uses Group II and they do not call it synthetic (Chevron is the largest producer of this type of base stocks). Penzzoil used Group II in its conventional oil lines and also do not call them synthetic. Castrol Syntec uses Group III (purchased from Chevron?) calls it synthetic. By the judge's ruling, it could be called synthetic.
This whole idea of Mobil One not being synthetic might possibly be nothing more than idea of the marketing people for one of their competitors.
I disagree here. Mobile 1 WAS NEVER a 100% synthetic because the 15 - 20% of the additive was dissolved in a dino carrier oil (full PAO synthetic oil cannot dissolve the additives). It was right on the Mobile 1 bottle of the old formulation.
The old Mobile 1 you used for 15 years did use a 100% synthetic base stock (PAO) and tests show it was an excellent oil and far better than other oils. The new "Tri-synthetic" mobile 1 is different and tests show it is not as good as the old (in relative terms due to the advance in oil technology) Mobile 1 and other oils are showing better results or closing the gaps.
Just to add another twist to this. Mobile Delvac 15W-40 was an excellent oil (on a par with Delo 400) as it used Group II base stock. Now Mobile has lowered its base stock by mixing Group I stock in it. I have compared all the numbers, and its pour point increases, Cold Cranking Viscosity is almost at the upper limit specified by API (6,000 cP and the API limit is 7,000 cP. Delo's is 3150 cP).
These are from my own research and readings from numbers off of the Mobile Website and also from some other oil sites. I am just a car enthusiast like you and actually hates Amsoil due to its marketing. I will probably never use it.
Do I use Mobile 1? Yes, but only when it is on sale at Wal-Mart for $17.88 per 5 qt jugs.