G George, see what you started!
For your V10 I recommend Mobil-1 0W-20W or 5W-20W The 0-20 flows faster in a cold engine and most wear happens on start up. If you are going to extend your drain interval from what the manufacture recommends you will need to do oil sampling/testing. The sampling tells you two major things what is the condition of your engine and what is the condition of the additive package. Well ok it will tell you if you have any contamination, antifreeze or fuel.
I would recommend sticking to the recommended change interval while in warranty. You have a nice coach.
Bill