Gas mileage & programmer !?

Tristan Durbin · July 16, 2019

I have a 2015 Chevy z71 5.3. Gets horrible gas mileage. Doesn’t matter if i baby it around or go balls to the walls. Only gets a good consistent 12-13 mpg. Any ideas? Programmer? Little tricks?

Jmanson6262 · July 16, 2019

Flex fuel or no? Clean that maf and run premium. If you have a way to reset your long term fuel trims do it.

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CamGTP · July 16, 2019

Too hard to say why without data logs or a video from a live data scanner than can show all sorts of information that could point to how it's running.

If flex fuel but not running "flex" fuels, the fuel composition could be stuck/reporting incorrectly and tanking the fuel mileage. Dirty MAF sensor, lazy o2 sensors, minor vacuum leaks could all cause poor mpg.

How quickly you drive and if you leave the vehicle idle for long periods of time will ruin fuel mileage too.

xSHIFTxNASTYx · July 16, 2019

Do you rely on the DIC for your mileage or do you hand calculate?

I'm running an experiment where I'm tracking my MPG but I'm hand calculating everything by the gas pump. I find my DIC for mileage is waaay off, by an average of 3-4 MPG or so. When it is high and seems ambitious, it really isn't... and vice versa when it is low.

Try hand calculating it sometime and see if it turns out to be a bit higher than 12-13 MPG.

Jacoby · July 16, 2019

How about you tell us about the truck. Is it all stock, lifted, bigger wheels, etc.

aseibel · July 16, 2019

51 minutes ago, Jacoby said:

How about you tell us about the truck. Is it all stock, lifted, bigger wheels, etc.

^This, and what speeds are you driving? There are people in Texas who go nearly 100 on county roads. So that would also tank your mileage while driving a brick on wheels.

Ozer · July 16, 2019

IF you are stock, then 12-13 is low. You def have an issue that needs to be fixed, no tuner or programmer can help raise that w/o getting the issues fixed.

I usually run 87 on mine and thats my baseline, i get 18-19 hand calculated per tank.

I tried 90 non-ethanol for one tank and the numbers dropped slightly, no real improvement.

Now im trying 87 Mobil gas, see how that does compared to Speedway 87 i get usually.

Try a different gas station, use Techron fuel injector cleaner, no other brand works from my experience. Its about $8 buck, run it back to back twice.