Amsoil believers tend to pretty emotional about the product. I personally have never used the product despite the urging of a few people I know. I have used Royal Purple for quite some time in both the 08 Bullitt and in my F250 Super Duty. I have no complaints or issues with Royal Purple. I run Mobil 1 in the DD and the Joe Gibbs "Driven" oil in the race car. So it depends on what I am using a particular vehicle for that determines what oil I use.