I have a 86 ex. cab 4x4 p/u and a 95 ex. cab p/u. I am running 30x9.5/15 a/t's on both looking to put 31x10.50/15s on them wondering the diff. in mpg.? any help would be great. (both are stock wheels)

 

Not a lot. It will also depend on the aggressiveness of the tread. Is it a M/T tire you are putting on?

 

I havent decided id like to have another set of bfg a/t's but i may switch to bfg m/t's if theres not a big difference.

 

Your not going to see a heckavalot of difference...I get 18-20MPG with 34" A/t's and 22MPG with 31" M/t's

 

not a huge difference, at worse proprtional to the change in tire size.
However, going from a bias to radial may increase your mileage, and likewise, going from a radial to bias could hurt your mileage.

 

i got better gas mileage on the highway with my 33's and stock gears. it got alot worse in town though but it is still better then my 31's i spin about 2400 rpm on the highway a just a hair under 65 i think, my speedo is off. overall your change is not going to be to much do i dont think its going to be very very noticeable better or worse

 

thank u guys for all the help.

 

If your driving habits are identical and you can accept the torque reduction I think tire size is less of a factor that tread. If you go to an M/T you can count on a lot more rolling resistance and significantly worse mileage.

 

Depends how you drive, if you try to accelerate as fast with 31s as you did with 30s, 28s, whatever, then you're going to notice a bigger drop. If you are as gentle with the throttle as before, then your milage will remain unchanged.

I have 31x10.5s and I went from 4.10s and I went to 4.56 - which is in effect a similar change to yours (except I'm improving the effective final drive, you're lessening the final drive). I got my best mileage yet (27mpg on a loaded 4Runner running 4.10s and 31s).

 

I have a 93 pickup with 3.0, 5 spd and stock 4.30 gears. When I bought the truck it had
33-12.50 Claws. Couldn't use 5th gear and was getting 13.5 mpg. Put on 32-11.50 BFG
A/T - got 5th gear back and jumped to 19.5 mpg.

 

Edit.

 

If they are street a/t's then I doubt it. Keep em at 35-40psi.

 

at least u get better mpg with 33's than me with 31's i get 12 in town

 

I am going to be running 32x11.50 bfg a/t s with 4.88s any idea what kind of milage i will get more or less with a 1984 pickup 22r. old school yota i love it 141,000 oroginal miles