I've seen folks state both 80w90 and 75w140. Which is the best choice? If it matters, I have 4.56s and this car is solely for backroads bashing with (hopefully) a few track days per year sprinkled in going forward.
And past that, any reason to pick one or the other between RP, Amsoil, and Red Line?
And past that, any reason to pick one or the other between RP, Amsoil, and Red Line?