# extremely poor gas mileage



## stickpony (Oct 26, 2008)

i just bought a factory certified '06 GTO with an auto tranny, bone stock, and i am getting 10 mpg in the city and 12-13 on the highway. ive driven this thing like miss daisy since i got it a week ago, but the gas mileage is still piss poor... anybody have any suggestions? maybe i need to reset the computer or something? 

any ideas?


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## alsgto04 (Nov 21, 2007)

Welcome to the forum!
Ill go on reset it, its too low maybe the other owner was driving it pretty hard thats why its like that. Good luck.


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## GTO JUDGE (May 14, 2005)

Find out if the car was tuned. Something is definitely wrong there.


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## Aramz06 (Mar 2, 2008)

Im getting 13 or so on city driving in L.A's Traffic!! How you get that on the highway is beyond me.


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## PDQ GTO (Jun 21, 2007)

Take her back and make them go through the car. Best place to start IMO. I get 9 MPG in town, but I know why...:willy:


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## GM4life (Mar 18, 2007)

Did you reset the computer when you fill up? What octane gas you putting in it?


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## silversport (Mar 23, 2007)

I do mostly city driving and short runs at that and my '06 is getting about 13-14MPG...21+ on the highway...good luck with yours...I agree on trying the reset...
Bill


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## stickpony (Oct 26, 2008)

silversport said:


> I do mostly city driving and short runs at that and my '06 is getting about 13-14MPG...21+ on the highway...good luck with yours...I agree on trying the reset...
> Bill


its a stock Ls2 motor and it has not been tuned. How do i go about resetting the computer and whats the idle re-learn and the driving re-learn procedure for this car? i know what it is for my '92 cadillac seville, but that was the OBD-I days, this is a whole different animal...


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## GTO JUDGE (May 14, 2005)

stickpony said:


> its a stock Ls2 motor and it has not been tuned. How do i go about resetting the computer and whats the idle re-learn and the driving re-learn procedure for this car? i know what it is for my '92 cadillac seville, but that was the OBD-I days, this is a whole different animal...


Fill your tank up.. then reset your computer. The reset is located behind the steering wheel to the right on the dash beside the radio. Toggle the display until you get to the mpg, then reset it. Gauge your mileage on bypass driving without interruption. Once you get to the point of refilling, do the math manually and see if the figures equal the computer.

The longer you go without resetting the mpg settings the worse mileage you'll get as it will read city, highway combined. Your stop and go driving will drive down the figure.


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## GM4life (Mar 18, 2007)

GTO JUDGE said:


> Fill your tank up.. then reset your computer. The reset is located behind the steering wheel to the right on the dash beside the radio. Toggle the display until you get to the mpg, then reset it. Gauge your mileage on bypass driving without interruption. Once you get to the point of refilling, do the math manually and see if the figures equal the computer.
> 
> The longer you go without resetting the mpg settings the worse mileage you'll get as it will read city, highway combined. Your stop and go driving will drive down the figure.


:agree To piggy back on what JUDGE said use your MODE button to toggle and use the SET button to reset.


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## 6QTS11OZ (Mar 27, 2005)

stickpony said:


> its a stock Ls2 motor and it has not been tuned. How do i go about resetting the computer and whats the idle re-learn and the driving re-learn procedure for this car? i know what it is for my '92 cadillac seville, but that was the OBD-I days, this is a whole different animal...


I normally just hold the "Set" button down after the computer (D.I.C.) goes through it's little check and shows the odometer reading. It will beep when it's reset.

Also you can just fill the car up and during the next fill up divide the total miles driven by the gallons you put in it and that will give you your true miles per gallons.


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## alsgto04 (Nov 21, 2007)

6QTS11OZ said:


> I normally just hold the "Set" button down after the computer (D.I.C.) goes through it's little check and shows the odometer reading. It will beep when it's reset.
> 
> Also you can just fill the car up and during the next fill up divide the total miles driven by the gallons you put in it and that will give you your true miles per gallons.


:agree


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## m289d (Nov 6, 2007)

I would just like to add a note to this thread. I found out that if you press the set button twice it will reset all gas mileage and trip mileage counters. You don't have to hold the set button down to reset unless you only want to reset the particular item that you are viewing at the time.


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## stickpony (Oct 26, 2008)

i think you guys misunderstand me.ressetting the counter will have NO effect on the variables the ECM ( computer ) uses to calculate the fuel trim. i want the ECM to be reset not the calculator that predicts my miles per gallon nor the counter that tells me what my current mileage is. I want to rset the ECM and have it relearn my driving habits so it can give me the best gas mileage.


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## Rukee (Feb 8, 2007)

The computer should making those adjustments hundreds of times a second to get you the best millage. 
The only way I could see the computer causing poor millage would be if the car had a bad 'tune', then flashing back to the original tune, or a propper tune could help.


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## 6QTS11OZ (Mar 27, 2005)

stickpony said:


> i think you guys misunderstand me.ressetting the counter will have NO effect on the variables the ECM ( computer ) uses to calculate the fuel trim. i want the ECM to be reset not the calculator that predicts my miles per gallon nor the counter that tells me what my current mileage is. I want to rset the ECM and have it relearn my driving habits so it can give me the best gas mileage.


If what we're telling you isn't helping then I suggest you take it to the dealer or a tuner and have them check the parameters within your computer to see what's wrong. If there is something screwed up with your tune then something as simple as disconnecting the battery to reset the computer will not help. They definitely need to look at your STFTs and LTFTs on both banks to see if the readings are positive which will indicate that it is running rich, extremely rich, etc. Good luck with that.


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## silversport (Mar 23, 2007)

or disconnect the battery for a bit and let it do the relearn...but it should relearn while you are driving...
Bill


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## rnoswal (Dec 2, 2007)

Just a few things to check. Air filter, tire pressures, any missing while driving. And as was asked before, what grade of fuel are you running? I have a manual tranny 05 and with regular and the AC on I could easily get 14 mpg, with a slightly heavy foot around town. No AC and it would go up to around 16 and with premium and no AC, it's cooler now too, I am getting around town. 

I could only afford regular since I bought it ealier this year and for the first time filled it with premium (93) last week. It runs smoother, the throttle is crisper and it feels stronger. I also replaced the plugs last week after 48K on the originals. You will get lower mpg with an automatic under the same conditions as a manual tranny. Try running the engine hard a few times. Carbon will build up in any engine and will hurt mpg, Fuel additives help, but you can tell when a car hasn't been run hard when you see lots of brown and black smoke coming from the exhaust when you follow behind it as it merges on the freeway.

Try a better intake system and a fuel additive if you run regular, or even middle grade. The knock sensors retard the timing with lower grades of fuel and that hurts mpg too.

Just my 2 cents

Russ


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