Yes it does, hence in the city you may see a little worse fuel mileage from all the starts. On the highway, since you do not have to expend the energy getting the bigger tire up to speed from a dead stop, you can benefit more from the lower RPMs it gives you at highway speeds.

 

So if I can recalculate the speedometer these 315's might work to my advantage?

 

Yes, right now your odometer is reading you travelling less miles than you actually are. If you make the adjustment to correct it, you should see an approximate increase of about 10% in what you are getting for your fuel mileage right now.

 

Just took my 315's of and re-installed stock 265's and my Mileage went down. (Speedo re-calibrated both ways and hand Calculated) I would put the 315's back on, but it's camping season and the 315's are only load range "D" and my 265 stockers are "E" rated...

 

I think that it depends on the tire. With aggressive the milage will go down. W/ more reasonable all terrains the milage will go up. Iwent from the stock 265s to 315 BF Goodrich all terrains, my milage went up 1 mpg. When those wore out, I replaced them w/ Hankook 315 mudders. They were even load e rated. The milage went down 1 or 2 mpg. Toyo now make a 285/75 (and not just a 70) which is what I will try next.

 

So how can I recalibrate my speedometer?

 

Some of the programmers, Bully Dog and Smarty, have an option to correct your speedo for different size tires. The dealership can also make the adjustment. Kinda widespread spattering as to what the dealership charges for this adjustment.

 

Go to the dealer.
I had mine reflashed for the 315's for a 12 pack.

Following the other responses, 315' DO worsen your MPG. Sure it helps give you more of an over drive, but its a heavier, taller tire. Figuring all that thats why I only went down under 1 MPG.