Originally posted by FordMonkey:


Synthetic products from Mobil (Mobil 1), Castrol (Syntec) and other major oil companies are typically made from Group III base stock (petroleum oil) rather than more expensive Group IV or V base stock (PAO or diesters).






Mobil 1 is Group IV. Mobil sued Castrol about using Group III base stocks and calling it synthetic and lost. Since then, others have introduced "synthetic" oils that are Group III, but not Mobil.


Jim Johnson 98 SVT 03 Escape Limited