I agree with the x-40w oil in the 2.7/3.5 family of engines. I know several people who have had phaser issues running 5w30 dealer serviced intervals. The issues with phaser rattle on these engines are well documented. I think long change interval, the micro soot for lack of a better term that is associated with direct injected engines that is documented wears on the chains and causes premature stretch. With a 40 weight oil the hot idle pressure is more consistent such as siting in traffic the phasers are less likely to loose pressure or have erratic pressure causing them to not stay in commanded position. These are all theories I have relating to these engines, I think Ford did a dis-service to their customers with their oil spec. I have ran M1 0w40 or QS 5w40 since my truck was new, 2015 3.5 doing 5500-6000 mile changes. 94000 miles on it now and it's done well. I think coolant changes are important as well, these engines run hot, keeping them cool is important.