2Easy,
No disrespect intended, just for discussion.
Anytime someone suggests a different oil than the manufacturer recommended oil type or viscosity - I always ask them what the piston ring end gap is and why it's that number. If they don't know, I suggest that the person that does know, recommended a particular oil viscisity and that they wrote it down for me in the owners manual. It's my way of saying that, in my opinion, the folks that really, really know your engine made an oil recommendation and that you should make sure the person telling you to do something different understands at least as much about your engine as the manufacturer does. FWIW, I really don't know who that would be.
Having said that, I've been running 0w40 based on a web discussion (on this forum) with the SRT engineers. They recommended 0w40.
Greg