Here's some background
oil info to plant the seed that it isn't just the base oil, it's the additives, also.
Even synthetics aren't synthetics anymore, as Castrol (and others) now markets a finished oil that can legally be called synthetic, but the original material comes from crude oil.
Castrol Syntec
Many base oil suppliers are developing information to show that formulating with Group III base oils provides equivalent performance as with "original" synthetics.
Group III base oils
How come the Group III base oil challenge to synthetic? SAE 5W20 oils, now factory fill in Fords and Hondas, require low temperature, volatility, and stability performance. How it is achieved doesn't matter, and with the only other choice being the more expensive synthetics, refiners have figured out how to get to the same performance from "crude" oil.
And finally, here's a page from a manufacturer of friction test equipment that coincidentally shows that among 9 oils used to show how the equipment works (8 synthetics, one mineral) the best and worst were both synthetics.
MTM Applications , sort of saying that a synthetic base oil alone isn't the automatic killer app, it's the complete formulation.
