The only "requirement" to comply with Ford warranty is a lube that is on the approved F1 spec (the current list).
There are a LOT of lubes on that list. Conventional, semi-syn and syn.
It is NOT "required" to run a syn, or a 5w-40, for compliance with warranty. Only that you use any lube meeting that spec.
Because that single spec includes 0w-40, 5w-30, 10w-30, 10w-40, 5w-40, 15w-40, etc, then ANY grade can be used, to satisfy warranty, as long as you use a product from the approved list.
What they "recommend" is not the same as what's "required".
Warranty statements and coverage are in compliance with the FTC M/M Warranty Act. Ford cannot deny coverage when you comply with the proper specification. They can delay coverage, if they want to, but an arbiter will not find in their favor.
https://www.fcsdchemicalsandlubricants.c...ory=Motor%20Oil
Note this link was last updated 3-5-18 (yesterday!)
That's about as current as one can hope for!
Remember, the M/M Act is about the burden of proof when it comes to warranty claims. Just how is it that anyone thinks Ford can successfully delay or deny warranty when they spec a slew of lubes, with all manner of base stocks and grades, all on one spec? When you comply with warranty by using a spec'd fluid, it is the burden of proof upon the OEM to show that you somehow caused the failure in question. How does Ford say "you used the wrong lube" whey they are ALL one ONE spec sheet?
As if this topic isn't
PS - there is no "best" oil, but you've probably already got your mind made up anyway ...