What exactly does "ECO" mode do? I took a 300 mile trip this week and averaged around 20mpg overall. I used ECO the entire trip. Seems to shift sooner and seems to be a bit sluggish. Other than that drives like normal. I think I would make this the default if Ford allowed that.

Also on another note, I hit around 85-90 once with maybe 1000lbs total weight in the bed and cab (evenly distributed - 4 passengers and luggage) while passing and truck was shaking a bit more than I feel comfortable with. Is this normal? I don't usually drive over @75.

 

very likely quickly short shifts to keep engine RPM down, very likely will adjust your throttle pedal to make it less sensitive so you have to push the gas further to get the TB to open, and very likely will put a delay on your throttle inputs to dampen your request for more throttle.

If your truck is shaking at speed you likely need to get your wheels/tires balanced. It should not shake at all, regardless of load. I've cruised down the highway at 80mph with 2000# of stone in the back of my truck no problem.

 

To get super technical the ECO mode does not allow you to go zoom zoom while saving you maybe 1 mpg. If you want to go zoom zoom you must put it in normal mode but to hit ludicrous speed use sport mode.

you're welcome

 

I don't have any vibration or shaking over 75 - completely smooth. First thought is possibly wheel balance or tire wear, but could be a number of things.

 

The tires are a bit worn (34k miles). I was planning on replacing them later this year. I will add an alignment to that. Truck is very smooth when it is just me in it even at 85.

 

Funny, I been driving my 2019 in Normal so far, but yesterday tested both the Sport and Eco mode. The Eco has the smoothest trassmission shifts so going to start using that.

The Normal mode has hard shift from 3-5 but not bad. The Sport has hard 2 to 3.

I really have no idea if that will help with the transmission or not, but is super smooth shifting in Eco.

 

ECO mode does cool the shifting vs throttle applications and change the shift points mainly at lower speeds through the first 5 gears in stop and go by design and even somewhat in Wet/Snow mode for better traction with reduced Torque reaction.
From gear 6 and up there will be little to no difference to fuel mileage once in those gears, the engine RPM is what it is at any given speed.
I use ECO mode when wife is on board because she does not like neck snapping in default mode due to s Spine issue.
If ECO were the default owners would complain. They already complain because it's not selectable as Default mode.
It is not made controllable for default but you have to select ECO. No problem pressing the shifter button 4 times without looking anytime I drive off. or 3 times for Wet/Snow mode when desired. The modes never change position in the line -up so you don't even have to take your eyes off the road to make the change.
As to vibration, there is something else going on.

 

I used ECO mode for the first 8 months I had the truck. In the end I stopped using it for one main reason. If I was stopped dead in traffic then had to jump out into the next lane, the hesitation was damn near a second a a half before the truck would go or find the right gear. Not safe in my eyes. It barely got me an extra half mpg anyways. Drive it in normal mode now

 

https://www.dorazioford.com/f-150-eco-mode/

 

That article is a classic example of something written by an AI. Complete nonsense sentence structure.
"acceleration feels slower when pressing the total pedal." And "less use of up and down a gear and accelerate paddle."