The 2010 Fusion in my signature specs 5w20, but here in Phoenix, it regularly goes over 115F in the summer, so I almost always run 5w- or 10w-30 in it during the hot months. it normally only sees 5w20 between october and March, and sometimes not even then. I've been doing this since it had about 180,000 miles on it.
It's over 243,000 miles so draw your own conclusions.
Then again, in many engines, 5w-30 will shear down closer to 5w-20 within a few thousand miles anyways. I suspect my Duratec 2.5 does this.