So some 3.5L things to note. Some time mid ish 2019 Ford quietly changed some things on the 3.5. When I bought mine October 2019 I wasn’t aware of these changes.
So first off up till mid ish 2019 the 3.5L like the other Eco boost engine family engines we’re getting black ABS plastic oil pans. I had figured mine had that also. But my first oil change I was super confused for a few minutes when I didn’t find a ABS oil pan under my Expedition. I googled it while laying under the truck with oil changing gear in hand lol. So to my surprise Ford had quietly changed to a cast Aluminum pan roughly mid 2019 production run. So I was pretty pleased by my random timing. Also the cam phaser thing that seemed to plague the F150 and Expeditions, after doing lots of digging I could only find some random off hand suggestions that it looked like Ford had tweaked the cam phaser parts possibly around the same time they went Aluminum oil pan.
So if your shopping new or newish 4th gen that’s definitely something to keep on your radar.
I know at least with the Platinum the big sound deadening cover under the engine makes it near impossible to do a quick visual peek for the ABS vs Aluminum oil pan. I think the FX has a metal shield where my Platinum has the sound card so likely the same deal making it a bigger effort to eye ball the oil sump?.
Due to the Biggest Buck in town charging my Expedition head on mid day when I only had 980 miles on the clock?

. And now COViD I only have 11,000 on the clock. Due to the Cam phaser thing and turbo oil type/quality and change schedule is pretty important. I’m about to do my 2nd oil change shortly at 6000 miles oci. Apart from having to pull the sound card off the bottom everything is easily accessible. My wifes Fusion is near identical regarding the heavy sound card screwed in under the engine.
I’m not super Brand fan boy specific, I’ve had 25yrs of Toyota trucks after 12yrs of Ford Truck prior to that, had in tandem with the Toyotas my DD and light road trip Subarus. Wife had a VW which I didn’t like. I bought a real barn find SLK350 for Grandpa back in 2011 and he drove it about 3 miles a week between his place and ours. I drove it work occasionally and wife and I would take it on kid free weekend trips up and down the Coast, its a late 05 and has 23,000 miles on it?. Yes it was a real barn find, parked in a barn with 12,000 miles on it?.
If I were to shop today for the Expedition I think the only thing I would do differently is knowingly check for the Aluminum Oil pan and go light color interior over black interior. Other than that maybe a anti Buck mounting device on the front end. Damn Buck hit me at a full run right between the headlights. I was only doing 30mph and stopped just sat there as the dumb ass charged right into me. Zero damage to the fenders, big head print in my hood and he was so kind to fold into a giant ball and go over the bumper and under the hood! $15,500 in parts! Nothing major bent except the radiator and top cross member, but all the plastics were toast, backs of the headlights were sheered off etc.
5 weeks at a top shop all Ford parts which were tough to get given how new it was. Grrrrrr