p235/85 vs 33x12.5 vs gas mileage?

[NASTY-LSX]

ok so i need to use my k20 4x4 no lift as a DD for a few month. I need new tires. I can replace my 33x12.5 or, I got some 16x7 steel wheels, i can put some p235/85 tires on. Would there be a big difference in gas mileage?? i have a turbo 400 trans. No over drive. I get about 11/12 MPG Now with 33's.(and thats NEVER flooring it LOL)

So does a shorter or taller tire get you better MPG? thanks

[donut]

You can use a shorter or taller tire to fine tune your rpm range. My mind says, go smaller.
Won't look as cool, but IMO, tires would be cheaper and less rolling resistance by going narrow. (I'm cheap and getting old. lol)

Don't think there would be a big difference in mileage, but it shouldn't be any worse. Maybe 1 or 2? Hopefully someone with some experience with this dilemma will chime in.

[b454rat]

A taller skinnier tire will work better than a fatter tire, more rolling resistance

[streetrodchev]

You probably won't notice much of a difference. These trucks just don't get any better mileage.

[cadillac_al]

I think the 235/85r16 tires will last longer on the highway but I don't think the fuel mileage difference will be noticeable. tough choice, cool vs skinny; I'm not sure which way I would go.

[nekkidhillbilly]

some instances a tall tire will help just depends on driving habits. a highway tread will always do better. lighter set ups will always do better.

[special-K]

I think you will see no difference. The added rolling resistance of the 12.50s will be cancelled out by the taller diameter giving lower hiway rpms. And,basiclly,it takes a lot more than this to affect mileage on one of these trucks. I had 33/12.50s on my '72 K2500 with TH350 and 4.10s and got 12.5 mpg. I now have 235/75s and mileage is the same. I don't notice any difference in power,either. I also had a '72 K/20 when I had the 33s on the GMC. The Chevy had same gears but 4spd with 35/12.50s and 400 SBC and it got the same mileage because the added torque cancelled out the larger diameter as well as direct lock-up at all times. I know because for a good while the odometer and fuel gauge weren't working in the GMC and I went to the same job driving the same route for a couple months and they both consistently used the same amount of gas after the same amount of trips.

[nekkidhillbilly]

i dont think its going to do alot different. which a truck with no overdrive 12 mpg is about right.