Window deflectors, tailgate dampener, tailgate lock, LED backup lights, black tailgate letters, hood deflector and maybe mud flaps are the extent for me at this time. Maybe in a few years my Rapid Red, lariat first edition will still be worth what I paid for it...HAHA.
I usually get my best mpgs in the fall when temps are low 70's. I drive about 400 miles per week (about 50/50 hwy/city) and am getting about 45/46 mpg every tank.
Right now on the Ford accessories site they are offering 15% off till 12/31/2021. Doesn't help us hybrid guys as our truck won't be delivered until after the first of the new year. I would buy my accessories now but want to wait till I can use my Fordpass points.
Rumor has it the hybrid buyers will get an additional 20,000 points. Using mine on floor liners, window deflectors, tailgate damper, tailgate lock and hood deflector.
If you get this keep EVERY receipt (even from Ford) as most plans are picky. Also if you are going to make changes (especially performance) you may have to notify the plan so you don't void the plan.
The best way to improve MPG is to change and fine tune your driving habits. Allow the vehicle to take off in EV mode till about 15 mph before speeding up. I use cruise control on my C max but can actually extend mpg by watching the battery guage and then raise your foot a bit to kick the EV...