Duane

Very good info Tony Raine. I'm sure other readers will appreciate your input as did I.

Lariat4x4

anything bigger than stock wheels and tires will negatively effect your mpgs period. Ford matches their 17", 18", and 20" rims with specific tires to garner the best mpg's possible. So bigger than your stockers would warrant worse mpg, just ask me how I know lol.

XLT Billy

How do you know Lariat?! lol. I have heard that before though.

Lariat4x4

I know because before I leveled my truck and mounted up 35's, I was averaging 20.2mpg with the cruise set at 60mph with stock 32"x9.5"x18" tires. Now I am averaging around 16mpg with the cruise set at 60mph with 35"x11.5"x18" tires. The bigger your tires, the more rotating mass there is for the engine to move, meaning the engine will require more power and fuel to move the extra weight which in turn lowers the engines efficiency. Also to go bigger than 33's, you will need to lift the truck a little and that negatively affects the mpgs because your causing more aerodynamic drag and that requires the engine to work harder and burn more fuel as well. That is why our trucks look like they are front heavy and slant forward so that most of the air travels over the truck and not under because underneath, there are too many components that reduce the drag coefficient. Ford's R&D team researches extensively to find the best engine efficiency for these trucks by experiementing with different tire brands and sizes and different rim widths and heights to try to maximize efficiency as best they can. So when you step out of the stock sizes, it does negatively effect your mpgs. The only thing I can think of that wouldn't, and dont quote me, is maybe going with smaller rims/and or tires. I hope this helps.

Duane

Thanks LARIAT4x4.... Thats some good stuff.