My average gas mileage for the last three years is slightly better than 35 MPG (6.7 liters per 100 km). Almost all of my driving is at the speed limit to 5 MPH faster in speed limits up to 55 MPH. And that is in the Northern Wisconsin climate. In a warmer climate my average would be about 38 MPG. In a crew cab pickup truck.
I do none of the things listed in the OP because those things do not work. What does work is DWB, DWL (search this site), grille block, aero topper, tire pressure, LRL tires, and a kill switch. The details are in this thread:
https://ecomodder.com/forum/showthre...yon-17070.html.
And the box of my truck contains two toolboxes, a box of tire chains, a container of sand, and some miscellaneous stuff. Plus a full size spare tire underneath.