jkp21

im currently running 265/70/17 and averaging 18 mpg on the hwy, if i go to a 315/70/17 how much fuel mileage will i use in town/hwy.. Also any other problems or changes i need to make? Truck has, level kit, programmer, exhaust..

18_F-150_XLT_Screw

iTrader: (1)

I went 285/70 and dropped about 2mpg (even after correcting for the tire size with a programmer to be able to calculate mpg properly, since the odometer would be off).. But mine are the heavy load e rating as well.

dufx4

The tire size in the programmer is to recalibrate the speedometer...not give you the fuel mileage back that lose from bigger tires.

dufx4

I have that same tire size. I get about 12-13 mpg. If you regear to 4.56 the city mileage will go up a little more and help with overall mpg.

rmp213

you're jumping from a 31" tire to almost a 35" tire. If you have 3.55 gears, I wouldn't recommend it. It'll handled them, but your truck will be really sluggish and your mpg will pay the price. Not to mention that's rough on your drive train. I went from 255/75's (31") to 295/70 (33.5") and I lost an easy 2 mpg. If you have 3.73's you may be able to get away with it with less damage to your power/mpg's

jerrybizzle

As Ryan stated, check your door jamb sticker under axle code and see what gears you have, if 3.55 your truck will be straining and sluggish. I know, I had 3.55s before my current 4.56 gears. I had 285/70/17 before my current tires which are 315/70/17. 3.55s and 33s are okay, but the weight and height of the bigger tires was too much for anything other than leisurely cruising. I tow and my truck down shifted to first on a mountain pass, that's when I knew I needed to regear or get a new truck. Pics in my album titled my truck if you are interested in pics. At work on my phone so it's difficult to add pics.