I'm considering putting some BFG A/T 315 70R17 on my stock early 2004 truck. I'm just wondering how big of a decrease im milage can i expect. I have the 3.73 gears with the 48RE. With the stock 265 mich's on I get 16-17 in town, 18-19 going 80 down the freeway, and 20 + on the highway. At 3.40 a gallon I would hate to regret my tire decision. Thanks for any info

 

My 285s made almost no difference in MPG. I have heard 1-2MPG loss with 315s and 3.73 gears.

 

Running 38's on factory gears with transmission reprogrammed. Getting about 19 around town and 22 on highway, atleast that's what the computer says.

 

in town mine went down a little , did not loose any on highway might have gained because of the rpm drop i average 18 - 19 on combo of town highway , straight highway long runs i get 20 - 22 depending on speed

 

If you dont think you can afford 1 or 2 mpg dont do these things were not intended to be commuters quit fretting set it up how you want and drive it til it dies

 

I did not see any mileage change when I put on the 315-70-17 BFG AT's. I did see a nice drop in rpm's at higher speeds, maybe it all balanced out?

CD

 

No difference with my 285/75's running empty, but towing i lost a good 1-1.5 mpg ........

Rick

 

Lost about 2 mpg when I went from stock to 35/12.50/17 Toyo MT's. This is figured after recalculating for the change of tire size. A buddy lost about the same when he went to 315/17 BGG AT's.

 

I lost some around town and gained on the highway by putting 265/70x19.5 tires on mine. It was about a wash for me. I definately do better on the long highway trips but it ended up about the same for my normal commute.
I know the higher gearing from the 34.5" tire hurt mine around town even more because of the slushy stock tranny. I am planning on a new modified tranny this winter and know it will help regarding the mpg.

Jeff

 

I put 315 on mine and gained .5 hand calculated in town.. I also dont drive it like I stole it very often. really helped on the highway cause I can now cruise @ 70mph 18-1900 rpm in stead of 70 @ 2150...

 

I lost about 2 mpg all the way around with my 35's.
Scott

 

I also lost about 2 MPG with 35s... But that also includes the 4.5 inch lift which I am sure doesn't help....

 

I did the Hummer H2 wheel thing... 315-70-17.. I have seen 2-3 MPG loss all around. This is all based on the overhead computer.

Also noticed a decrease in braking performance. The ride was better, less bounce and bucking. I do have the Bilstein 5100 on.

 

I wonder if this is why my old Duramax got better MPG than the Ram in city driving, but worse on freeway? That thing had friggin donut tires on it...!

 

I lost about 2mpg all around going from stock to 285/75's