I have had BF Goodrich 315s (on H2 rims) on my truck for half a year. I get 20 mpg overall. This is realistic milage - I have kept track of every ounce of fuel poured into the tank. (BTW, I drive really light & the 20 MPG is mostly 50 - to 60 MPH driving w/ a few traffic lights - the milage goes down a little on pure intersate driving).

With fuel getting over $3/gal., I'm debating about putting the stock wheels back on. I'm guessing that milage will increase by 1 to 2 mpg. Anyone have data on what the milage difference between the two tires is?

 

I have run 265's and 315's both recently........interstate driving right at 70 and I can get 18 out of either. Actually, I got 18.2 from the 315's and 17.8 out of the 265's. These runs were within 3 weeks of each other, hand-calculated, and filling the fuel neck full.

Waylan

 

You may get a little bit more MPG but also take into account if you take it back to the dealer to get your Pinion Ratio fixed again for the 265 tires (if you did for the 315). That might cost a couple of $$ so over all, are you really saving $$ in mpg at all.

 

And if you didn't correct for the taller tires are you figuring in the millage error between 265s and 315s? If not that is 10% error in your favor.

 

i was able to get 23 with my 265's and a stock truck. now i get 17-18 around town and 19-20 on the highway if i take it easy.

 

PsRumors,

There is a 8.7% difference between the 265's and the 315's, and a 13.1% difference between the 245's that came stock on my truck and the 315's..........and yes, I take that difference into account.

Waylan

 

My mileage went down 1 mpg with the 315s...I can still get 22-23 mpg hwy if I can slow down to 60mph... NOT!!!

 

Why did you buy this truck would be my first question?
Honestly I bought mine because I have always wanted a full size 4x4 truck and I have a good history with Diesel and they are less maintenance and better gas mileage than their gas equivalent.

I had the stock tires and found the michelins to have terrible traction on these trucks and went to the 315's for looks and went with the T/A BFG's because I think they have great traction.

Yes, I knew I was giving up some fuel mileage but if that was going to make all of my decisions I would have went with a VW 4 cylinder diesel getting 50mpg.

LIve once, do what makes you happy...
Of course this is coming from someone who rides his motorcycle everyday to work because fuel costs too much

 

did you change the gears

you may actually see and increase in gas mileage with a slightly taller tire on a diesel because it will raise your efeective gear ratio and lower your rpms slightly

unlike a gas motor that needs a gear chaneg to keep it in its power band most diesels can handle a small increase in tire size with out giving up gas mileage

the differnce in roling resistance may eat up some of that benefit

if you added a lift with the tires then the increased wind resistance may be you mileage killer not necessarily the tires

 

id get a gps and confirm that difference.on paper,its supposed to be about 13%..but in real world,mine came out to 10%...from 245`s to 35`s.....10% across the board.showing 40-really44,,,50 really 55,,,60 really 66,,,70 really 77..........ive checked it against more than one gps,and thats what mine is.........bama

 

and by the way,,i lost 1 to 1.5 mpg going to the 35`s.thats mixed driving,towing and empty............bama

 

Guys, all this talk about "GAS" mileage is a moot point. Our trucks don't burn GAS. They burn diesel as we all know. The term is FUEL mileage!!!

 

I guess if you've had both sets of tires on the truck and have kept track of every ounce of fuel poured into the tank - you should be telling us the difference!

I've averaged over 17.5 over 125+ fillups since new; but its apples to oranges since our driving styles probably differ.

 

bama,

The 13% I quoted was from cooper and bfg literature. Using a gps, mine actually came out to 12.7%. I'm 4% over with 265's, 8% over with 285's, and 12.7% over with the bfg's. Only thing I don't like about using a gps is you are still referencing it to your speedo or tachometer, and you really don't know the calibration of either.

Waylan

 

I would be able to BUT...
The 265s were on the first 6000 miles (before the engine was broke in) & the truck has had two reflashes. The 18-037-04 helped moilage ALOT. Anyway, going by my fuel log, my milage increased from 17 to 20 between the time I had the 265s on & now. I'm not complaining about 20 mpg, just wondering how much more I'd get if I went back to the stock tires. I may have to put them on for a couple of tankfuls to find out.