MIELAGE.. sucks

[Hezsus]

Well the gas prices are hitting hard here, and it hits real hard running 93 oct and still getting 12-13mpg (mainly hwy). I fear i have something wrong. trucks a 98Z71 ECSB 355 vortec, mild cam, hooker headers, full msd ignition, K&N drop in, 285-75/16 tires. 3.73 gears. Black Bear performance tune.


what kinda mielage is everyone else getting?

any tips/suggestions for better mielage? I do monitor my driving as well

 

[Aloicious]

I got 14-17mpg stock in my 96 c1500, I get consistant low to high 15s with the specs in my signature. I would expect you to get a little less with a z71, your numbers don't seem abnormally low, but I don't see why you wouldn't be able to get a few extra. when is the last time you did a full tune up with fuel filter and distributor cap and rotor? if its been a while, I'd do that, otherwise try keeping your foot out of it.

 

[Sepiroth]

What he said.

Also, run a live scan and view your O2 values.

 

[jeff's88silverado]

mine gets 18-20mpg if you drive it like a normal person but if i drive it hard its more like 16-16.5

 

[Hezsus]

rears are tuned out, i'll get the fronts though, i know my fuel trims are completely diferent from bank 1 to bank 2 and my timing is pretty advanced, like 20-25+ on idle

 

[99z28monster]

runner smaller tires.

 

[Aloicious]

20-25 is normal, I have mine set around 29 at idle.

rears don't do anything but check cat efficiency. however if you're fronts LTFTs are very different alot of the time, then something may be up, you can look for exhaust and/or intake leaks which both would cause bad mileage and trim variability.

and yes, the tires are also contributing to the mileage.

 

[Hezsus]

fronts are both running at like .475-.485 the averages dont have more than .05 between them on average. the live values.. hard to record while driving but they run diferent, anywhere from like .2-.8+. i know that cyl 4 fouls plugs, and i have a tick, either exhaust or a real loud lifer. aside from that the engine has had the usual tune up plugs, wires, cap, rotor.

 

[Aloicious]

voltages and STFT's will bounce around ALOT, those are nothing to worry about, its the LTFT's and averages that you'll mainly want to watch for differences. it sounds like they're okay. if cyl 4 is fouling plugs its possible you have an injector leak or something there. and if you have an exhaust leak as well, that could be contributing to the problem. either of those may be the differences you're seeing.

 

[Hezsus]

voltages and STFT's will bounce around ALOT, those are nothing to worry about, its the LTFT's and averages that you'll mainly want to watch for differences. it sounds like they're okay. if cyl 4 is fouling plugs its possible you have an injector leak or something there. and if you have an exhaust leak as well, that could be contributing to the problem. either of those may be the differences you're seeing.

Great, thanks for the info, i never though of an injector leak. makes sense though. probably a cambination of that, larger tires, extra weight. ect. would an exhaust leak down the line.. after the collectors cause an issue?