All I know is that amsoil makes a premix 50:1 and 100:1, I am pretty sure they are a little different, but dont quote me on that. If I was going to run amsoil at 50:1, I would get the 50:1 premix instead of the 100:1. I run Belray MC-1 in my 3Ws, but on my 157 I am going to try the motul 800 as I have some once its broken in