I use Amsoil in my vehicles and have no problem with it. However, if you compare the specs for Shell Rotella T6 5W-40 to a comparable Amsoil product, the Rotella specs are head and shoulders above what Amsoil offers.
I use the Rotella T6 in my Kubota L47, my Husqvarna ZTH-6125 and all 4 stroke...