Hey what's up everyone, haven't posted in little while. So I have a friend who was one of the first people to buy a C36 in late 1994. Since he bought his car he's been using AMSOIL and recommends that I use it as well. I have a 97' C36 as you all know, but I don't know too much about AMSOIL. I do know, the guy I bought my car from told me that he's been using Mobil 1 Synthetic 0W-40 since he bought the car, so that's what I've been sticking with. AMSOIL recommends using their AMSOIL 5W-40 european motor formula and supposedly you're only supposed to change it every 10-15k miles... Any input?