my last car called for 5w20, and i regularly ran 0w20...but didn't grab a UOA...but the ol' "Butt Dyno" said it really liked the 0w20...
this car calls for 5w20, but judging by the writing in the owner's manual, it looks like the old couple who owned it previously ran 5w30. (in shaky handwriting it says "Best Oil, Castrol 5-30")
oops. the ford dealer changed it when i bought it, so, in theory MC 5w20, and this last(current) change is Havoline syn 5w20...
the model year after mine this same car & engine called for 0w20... take from that what you will...