The Redline and Amsoil arent sold locally on the shelf. At least not for the engine. My local dealer is also a FRPP dealer and their Shelby techs reccommend Mobil as its a synthetic. To use 0w or 5w. Thats what I was told by them anyway. They said due to the tighter tolerances in these newer engines and the variable cam timing that amsoil isnt a good choice on a molecular level.
Dont get me wrong. That didnt sound correct to me. But my warranty is on the line and I dont have 8 grand laying around for a new coyote if mine bites the dust and the techs say it was due to using 10w-30 or amsoil. This is my daily driver.
Not to turn this into an oil debate but the Mobil of today is not the same formula of years ago and Amsoil warranties their oil/engines so I can't see that being an issue...and Mobil one is not a true syn like Amsoil is so you were correct in your thoughts that they are full of shit.