Trying to find out why I've been getting poor MPG in town. In the city I get 10-12mpg, HWY is 18-20 pretty consistantly. I drive like an old lady and the valet switch is on 90% of the time so the 0plate really isnt part of it. The starwheel is spun back (towards rear of vehicle) a little more than halfway. No boost leaks, no fuel leaks. And the figures above are corrected 8% for larger tires (255/85 16's).

Back when I put in 370's I bumped the timing up to 16* now that I'm back to 160 sticks I wonder if this might be a problem and am thinking about dropping the timing back down to 13-13.5. Stock timing was 12.5*

Any thoughts?

 

how did you come up with 8%? i have 36" tires and have figured i'm off roughly 10%, but that's just by watching mile markers and my odo...

 

Well 8% of 30.5 (stock tire diameter) is around 2.4, add that to the 30.5 and you get 33" which is right at the height of the 255's.

 

33x5x16s. I wouldnt think your timing would make that much of a difference from where you are at now. Your only talking 2.5-3 degrees. I could and have been known to be wrong before.. What does it do with the Valet off?

 

I've been too scared to try it that way, fuel's too expensive lol

Only reason I'm asking is because its the only thing I havent changed in an effort to get better MPG.

 

Zach

ive never had a valet switch on my truck, nor do i know what its like or what it consists of for that matter, Now im thinking, i actually get better mileage with all my stuff full forward, but i guess its also cause i row my gears and i know how to get some good mileage with my truck

it kinda makes sence to me that if you are excluding the plate from the equation ur actually using more fuel to get to where you are going, wheareas if you were running everything as is, perhaps u might get better mileage? I mean more pedal pressure without the plate equals to more fuel being used, and in the highway i can see why it helps


im just thinkin outloud, id give it a try with the valet off...

Rick

 

Try it with the valet off. Since you don't have hugh bomb's it shouldn't hurt you to much and you might even gain alittle.

 

Before you blame the truck pick up a hydrometer and check your fuel. I have seen quite a bit of fuel with low viscosity lately. The other common problem in the spring is wax deposits on the injector nozzles, and running a tank of treated fuel will generally clear the problem.