Quoting myself here, but I just change the Rotella T6 15w40 after 5000 miles. A little longer than I wanted to go but all seems fine. So I can say that this is my new go to oil for this bike. I have been in a broad temp range from high 90s to high 30s and have experienced nothing but good.
So a couple of things I got the same amount of oil out as I put in, this is good, but I also had the same result with the Honda GN4, I experienced no issues with clutch slippage or any clutch operation and lastly with shifting there was a significant difference over the Honda oil especially after 3000 miles. From the time I changed to the T6 to the time I changed it out after 5000 miles shifting was smooth and quiet and no noticeable difference in operation at the time of oil change.
So I am sold on this oil and what is really nice since my wife and I are full time RVers as well I can get this oil at any Walmart. This availability of oil allows me to change my oil as needed on the road, as I just did in the middle of Death Valley.