I have used Amsoil in my previous cars, and will absolutely use it in my XF. I am interested to see the difference it makes versus the Mobil1 that's in there now. In case you haven't read this:
Royal Purple vs AMSOIL
I was debating on Royal Purple, but after reading many reviews on this Amsoil vs Royal Purple in different forums, I am sticking to what I feel confident with. Amsoil all the way