Amsoil also did endurance tests on it's oils, such as over 400,000 miles in a truck and it was still well within NEW wear limits.
OIL is changed way too frequently, even AMSOIL state a 25,000 mile change interval.
I have yet to read anything good about CASTROL RS 10/60 which I have used myself, for a week, never again, I read independant tests as no point reading a lot of them.
tabetha