Only use 5W20. Because of tight clearance tolerances in this engine, do NOT use anything higher than 5W20. When I first got a Ford that said 5W20 I thought to myself, that is like using water. After thoroughly investigating, I now understand the reasons. I used full synthetic because I have never had the same luck with American made engines that I have had with foreign made engines. I had a Honda Accord that had 209,000 miles on it when I sold it and still did not use oil.
Ford also allows 5W30 in this engine as an alternative if 5W20 is not available.
Congrats on your new 'baby'. Here's some useful info for you.
FORD has an RV division which can be reached at 1.800.392.5952
They have been extremely helpful to me and will put you into their data base. They recommended to me that I use Mobil 1 Synthetic 5w-20, which I use now. They will also direct you the the owners manual page should you need one (for free).