Oddly, I searched and saw only minor reference to this sorta big deal that impacts this era 5.0L (and maybe, it's unclear) 4.0L Explorers. But not the 2001s. Read the TSB. It's very difficult to interpret about the 4.0L Explorers.
Ford's Technical Service Bulletin states that a lot of models formerly recommended for 5W30 are now recommended for 5w20.
This is interesting. I recently purchased a LOT of 5W30 on sale at Costco. Thankfully, I have other vehicles that can use it. I also purchased a LOT of 5W20 for a couple other vehicles. Now I just have to make a mental note and probably change it in the owners manual and on the engine.
I recently took my Explorer to a nearby Midas that offered a free semi-synthetic oil change coupon. I was unaware of this TSB. As is good practice, I confirmed with them what they were putting in - a Wix branded filter and IIRC Castrol semi-blend 5w30. They did a great job. When I got home and was filing the paperwork, I noticed the actual mechanic put in 5W20. I called them up, and they hinted it's changed but did not explain or show me the TSB, so they drained it all out and refilled it with 5w30.
To their credit they took a "customer is always right" approach. But in this case I would have liked to have been told I'm wrong and shown the TSB.
Anyway, before anyone else makes a similar tool of himself (or buys a big amount of 5W30), be aware that Ford has retroactively changed recommendations on a lot of its older vehicles.