You supposed to calculate that yourself!

 

I tried, but negative numbers aren't cool.

anyhow, I think I got it figured out.

 

well i dont know what im doing wrong because i have 33 12.50s stock gears and im only getting 11 mpgs on my last 2 tanks.
Its an auto if that makes a difference.
Im going to do a tune up this weekend mabe that will help.

 

I think you've correctly identified the problem

33"+stock gears+auto = bad gas mileage.

A tuneup never hurt anything but it will not fix your problem.

 

If you have re-geared and changed tire diameter then you need to account for these changes when you calculate mileage. The odometer will not read the actual distance travelled. This was mentioned above but to start you need to make sure you are actually calculating the true MPG before you start troubleshooting.

I have a stock 3.0 5speed and get 22mpg on the highway, which I check after every fillup.

 

10 to 11MPG 94 pickup extra cab 3.0l auto 33inx12.50 tires stock 4.875 gearing 3 inch lift. Newly rebuilt motor top and bottom. and it got about the same before the rebuild. I need to get more MPG thinking of getting smaller tires but need to do tire and rims since they dont really make anything small for the rim size.

 

PSI
Fuel system (injectors, filter etc etc)
Those are two major things to think about when it comes to fuel economy in a 4x4. When i run 265x75 Toyo Country MT's @ 43 PSI i can get 25MPG in my 3.0L 91 4Runner