I have been reading up a lot on the GC oil. My BMW is due for a change, and the dealer seems to have had a change in heart about using Amsoil. Since the oil cap says Castrol, this seems like a match. Also, my daugther's new Envoy is up for it's first oil change and requires GM 6094M oil, which it has been recommended that a GF-3 oil will meet so again a good match. One concern I have is the barrier protection. While GC seems to turn in very good UOA's, how does it achieve any barrier protection without Moly or ZDDP? Is it the ester's? Just want to make sure I am making the right move to this oil for two very expensive cars.