As I understand it, even the "full synthetics" are not necessarily all synthetic. I would be surprised if companies like Royal Purple and Amsoil cut that corner, but others do. It's about as bad as trying to find a "good" battery anymore.
FWIW, Mobil 1 used to be considered the best (at least among the "bulk" manufacturers), but as I recall, their formulation changed a few years back, and it was questioned as to whether it was as dominant anymore.
FWIW, Mobil 1 used to be considered the best (at least among the "bulk" manufacturers), but as I recall, their formulation changed a few years back, and it was questioned as to whether it was as dominant anymore.