Here are the oil grade recommendations directly from the 2020 Ford owners manual. Nothing new but they do allow 15w40, 5w40 and 0w40, (as well as 10w30 and 0w30 for normal usage).
Do you think your post is less odd than his? I've seen the chart before, so it isn't new information to me I opened this thread thinking it might be about a specific oil he likes to use in his 6.7L. I didn't find what I expected. No big deal.
Your post though......it's a very odd first post. I predict you might not be here long.
On topic, @Snagglefoot
Do you have a new 6.7L Scorpion?
I Just switched over from the 10w30 factory fill in mine at 3000 miles, to 5w40 Rotella. Gets a hair too cold here on occasion to keep the 10w30 in over the winter. I'll run it year round for simplicity.
Haha, I was expecting you changed from 10w30 to 5w40 because you wanted a higher operating temp viscosity, not a lower xW viscosity. I was not expecting it.
The older manuals would cut Xw30 at around 90°f then go to a Xw40. My 75 LTD says to us Xw40 in extreme heat or excessive highway use. Oils and engines sure came along way in 45 years.