Indeed, as another poster pointed out, Amsoil has almost a cult like following. I have a buddy that has used it for years. For a long time her was a "dealer" of it. Something that I find noteworthy ( although it may not be related to his used of that brand of oil ) is that he has a twin turbo Audi sitting in his workshop with both turbos failed. Inadequate oil ? I have no idea.
Personally, I never have use Amsoil, and would not. I use Mobil One in my Nissan truck and in my motorcycle. I use Motorcraft ( which is semi-synthetic ) in all the Fords here.