I am just asking what you are trying to gain. If you trust the Amsoil rep and there is no measurable difference between 0W-30 and 5W-30 in temps above sub-freezing then there would be nothing to gain by using it, unless of course if it's cheaper.To be fair, it just comes down to how I personally make decisions. It's not about my ability to afford it, goodness knows my business has blessed me financially but it's the fact that if the additives are within the SP API Spec, and the viscosity is not an issue for where I live, then why would I spend double on the oil, that's really what it comes down to. I teach my 10 year old that success is all about living by making optimal decisions, so I have to lead by example, and that's all it really comes down to. For better or worse I'm almost (yes there is room for changing my mind) 100% satisfied with the decision. The only reason I hesitate, and only slightly is the fact that Amsoil does recommend the signiture series 0W30, and not the OE, but if they're both API SP, I'm just not that worried. Also, I don't want to get into analysis paralysism... guess I'm already kind of there.
The risk is (however small it is) that if you are under warranty and something goes wrong internally in your engine or Multiair module (that does happen) and the service department asks you to prove you've maintained the engine...how are they going to respond when you produce receipts from an oil that is both an incorrect weight and that does not have the required certifications?