hey
i am getting like 14.5-15 mpg highway with a/c going and 75-85 i feel this is not very good at all some help please i have 97 4x4 5-speed with 315 75 tires the engine has #10plate all the way forward, 3gsk, 370, timing 16-16.5, hx35/40 with 18cm2 straight 3" bhaf. i have been thinking about siding the plate back, and new fuel filter and fiter is pretty new. any help please
david

 

What gears?

 

3.54 gears

 

i have the same truck, same size tires, but lifted and stock motor and now get just about 20mpg highway. sounds like it may just be a matter of your mods and high speeds. optimal fuel efficiency is usually closer to 60mph from what i've heard.

 

Slow down. Is your spedo corrected? That will skew the numbers.

Slow down. MPG is never gonna be good at 85. Remember you are driving a vehicle with aerodynamic properties similar to those of a brick.

 

that's right. i forgot to mention, if your speedo is reading 75-85, you're probably actually going more like 80-90+ with the bigger tires, unless you've corrected for that

 

the speedo was off when i bought the truck by about 10 and i am pretty sure it is on right know i know the speed is killing me i will be going home tomorrow i it is a 7-8 hour trip that is why i go at those speeds because it can change hour- 1/2 hour but i just changed the fuel filter and slid the plate all the way back and i am going to see what that does but i have been thinking about changes those injector back to stock you think that would help a lot
thanks by the way
david

 

David you should update your signature to show your trucks year and mods. I am running a #8 plate (full forward), starwheel in the middle, 80 HP injectors, 4" inch exhaust, 3K Gov springs, Cold Intake, 315 tires with a5 speed and 3.5 rear gears. I will get the same mileage if I do not keep an eye on my right foot. If I drive 65-70 I will get around 18.5 - 19 on the highway. Anyone running 315's will need to add 9.349% to their total mileage then divide by total gallons used.

Dave

 

You could also try backing off the starwheel some, less fuel at low boost.

 

If your handle is any indication of your driving habits - and it usually is - try duct-taping a fresh egg to the go pedal, see if you can make the trip with the egg in an uncrushed state.

 

I have the 94' with #8 plate, from 60 to 70 mph I can maintain 22mpg but after 75mph it drops off fast.

 

im getting 14-16 mpg with quite alot of playing

 

going there with a strong head wind plate all the way back going 75-80mph got 13.1. coming back with some town driving pretty good tail wind plate all the way forward 70-75 got 15.8 very little playing i was mostly going 70 about 1900-2000 rpms. also put a new oil filter on.
david

 

Glad it's picking up. Can the overflow valve cause a milage drop?