The recommended oil is 5W-30. The manual states 10w-30 or 10W-40 can also be used as long as temps are over 0 degrees. The tolerances are much closer in newer vehicles so the heavier the oil could actually work against you. In the old days it wouldn't hurt to use heavier oil.
If you do a search for "0w40" you should get quite alot to read.
You should be fine with M1 0w40. I ran it for 2 oil changes with no issues.
It is on the lighter side of most w40 oils which works well for our trucks. I ran it in sub zero temps during the winter and <100 deg temps in the summer with no difference from 5w30 synthetic oil.
As Clint stated the recommended oil is 5w30. So running 0w40 would actually provide a little better protection for hot climates over 5w30 oils.
I recently tried Pensoil European 5w40 in my titan and I have noticed it is harder to start, even now that it is summer here in CO. The PP 5w40 is about average weight for w40 oils which based on my observations is too thick for our engine. I'm switching back to 5w30 or 0w40 at the next oil change.