I voted 16-17 because that's what I got doing my daily driving around town in Texas with the A/C on. When I drive on the highway, I easily get 20+.

 

Damm something must be wrong with my truck them. i get city 14 but highway 19-20

 

I have a 2003 Chevy Blazer, 4x4, 4dr. I can get around 15.5 mpg when it is cold and or stopping and starting too much. Up to 16.8 mpg with not much stoping and starting and longer drives. The best I did for almost all highway driving, nice day, no a/c, 60-65 mph average, and only the driver in the vehicle is 24.5 mpg. Otherwise, I can do between 21-22 mpg.

 

so i guess i get somewhere around 14 with 31x10.5 MT's

 

After doing all the math a figured out that I am getting a hair over 18. I went from 235/70/15 to a 31x10.5. My od. is off by 10.79% now so when it says that i am doing 54 I am actually doing 60. I really want to get everything fixed so that it reads right, but I can't find anywhere around me that does it.

 

Dealership or a computer programmer are your only real options for that one...

 

Ok after my tuneup and my front differential and transfer case fluid, I now get 17city 22highway with 4.3L AWD 3.73 rearend.

 

about 18 combined. don't use a/c for 2 reasons. # 1 i live in Canada ( we live with snow all year round) and #2 the a/c needs to be recharged. BTW forget about #1.

 

18MPGon the last highway trip... 74+ MPH the whole trip AC on/off depending on how I felt, lol.

BTW, living in Canada is no reason not to use AC... It still gets frickin' hot here. lmao.

That's with 30x9.5" BFG A/T's and 3.42 gears...

Truck came with 235/75 R15s. Got 24 MPG on the last trip I did with the factory rubber at the same 74 MPH, lol.

I wonder if 235/70 R15s would give me better mileage...

 

If you're after mileage go with the 205/75/15s