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Discussion Starter · #1 ·
I have a 2011 AWD Denali 77,000 miles getting 9 miles per gallon. Just did oil change and tire rotation. Air filter brand new. What would cause my truck to get horrible gas mileages?
 

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I have a 2011 AWD Denali 77,000 miles getting 9 miles per gallon. Just did oil change and tire rotation. Air filter brand new. What would cause my truck to get horrible gas mileages?
There are a number of things that could affect MPG. First, have you had anyone connect an OBD scanner up to the under dash port to see what fuel trims are, 02 sensor readings are, etc?
That would help determine if the fuel/air ratio entering the engine is proper or not. Even a leak in the exhaust system might cause some issues.
Has the engine throttle body been cleaned lately? Does the engine perform ok?
Any rough or uneven idle problem?
You could take it into one or more auto supply stores ( Autozone, Advanced Auto, etc) that might connect an OBD scanner to your Acadia and see if any codes are set.
 

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Where are you getting 9 mpg from?
Hand calculation
DIC.

if from dic, do you reset at every tank fill?
 

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Determining actual/realistic mpg requires patience. You need at least 3 fills (from low fuel level) to get calculation. This is because the auto shutoff will vary between pumps and even on the same pump. Three fills helps even out this potential error.

George
 

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Determining actual/realistic mpg requires patience. You need at least 3 fills (from low fuel level) to get calculation. This is because the auto shutoff will vary between pumps and even on the same pump. Three fills helps even out this potential error.

George
We hand calculate the MPG at every fill up and compare to the DIC readings.
Over the years it usually is withing 0.2 to as much as 1 MPG difference.
Most often though . . .the DIC reading and hand calculation are within 0.5 MPG.
 

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Discussion Starter · #6 ·
There are a number of things that could affect MPG. First, have you had anyone connect an OBD scanner up to the under dash port to see what fuel trims are, 02 sensor readings are, etc?
That would help determine if the fuel/air ratio entering the engine is proper or not. Even a leak in the exhaust system might cause some issues.
Has the engine throttle body been cleaned lately? Does the engine perform ok?
Any rough or uneven idle problem?
You could take it into one or more auto supply stores ( Autozone, Advanced Auto, etc) that might connect an OBD scanner to your Acadia and see if any codes are set.
Throttle body new
O2 sensors I replace them at least 12 times a year same with the Cats 4 times a year plus y-pipe 2 times a year.its been in sooooo many shops no one can figure out why my exhaust keeps going bad. Engine runs like new snappy throttle
 

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I have a 2014 GMC Acadia with 97,000 miles and I’m having the SAME ISSUE! No codes, no ruff idle, no hesitation or stalling. Cleaned the throttle body, cleaned the MAF sensor. New air filter, new cabin filter, new spark plugs, oil change, new tires,(all correct pressure) alignment done, all fluids changed out. Checked all breaks and axles to make sure nothing is dragging.No change to fuel economy.
Done by hand, resetting the in vehicle reader, also using Carfax calculator at every fillip at the same station. Always between 9-10 MPG. (This is mostly city driving not highway for context).
The next things I’m going to have checked to try to figure it out is if the intake is clogged due to it being a GDI engine. (But the engine sounds fine????) or if there is some exhaust issue dispite no real outside indication that would be the case. If you haven’t checked any of the things above, they are things that can effect fuel economy.
I’m taking a break for a bit in sinking money into figuring this out.
But if I find a Mechanic who can figure it out I’ll let you know.
 

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When was the last time you changed the spark plugs? Our 2014 is getting 22 hwy around 15 city, 17 avg.
I bought it 3 months ago, did all the things I listed in the post within one month of buying including changing spark plugs. (Paid a mechanic, didn’t do that one myself) like I said can’t figure out why the MPG are so low.
 

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I have a 2011 AWD Denali 77,000 miles getting 9 miles per gallon. Just did oil change and tire rotation. Air filter brand new. What would cause my truck to get horrible gas mileages?
It’s hard to tell anything with city driving numbers.

hit the nearest straight highway, set cruise control to 70-75mph and reset the average MPG reading. Are you getting the advertised 20mpg +/- ???

My 2013 Denali returns a solid 21, 22mpg on our road trips with 2 adults, 3 kids and loaded trunk going 75mph-80

around town wifey averages 14-16 driving the kids around.
 

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I have a 2011 AWD Denali 77,000 miles getting 9 miles per gallon. Just did oil change and tire rotation. Air filter brand new. What would cause my truck to get horrible gas mileages?
I would clean the intake valves. Due to direct injection they get very sludged up. This restored my gas milage. I used stp valve cleaner by direction on it.
 

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Discussion Starter · #15 ·
It’s hard to tell anything with city driving numbers.

hit the nearest straight highway, set cruise control to 70-75mph and reset the average MPG reading. Are you getting the advertised 20mpg +/- ???

My 2013 Denali returns a solid 21, 22mpg on our road trips with 2 adults, 3 kids and loaded trunk going 75mph-80

around town wifey averages 14-16 driving the kids around.
Don't have Cruise control due to my brake light is on
 
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