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Discussion Starter #1
I have a 2009 G8 GT with 93,000 miles on it. No codes showing and running fine except for one thing....I'm only getting 5.6 mpg city and 16 hwy. What could be the culprit? Latest OEM parts added were a radiator, upper radiator hose, radiator cap, battery, brake pads all the way around. Non OEM was a new full headliner.

Guys can you point me in a direction that I can resolve? :-(

BTW, no leaks in any of the lines on a visual inspection, no loss of power. Running Sunoco 93 octane always.

Thanks
Ras
 

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Is the car all stock other than what you wrote above?
 

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Are you calculating MPG's by just reading the cluster display or are you tracking your miles driven divided by tank fill up's and taking an average? 6 MPG is very low even for city driving. No mechanical issues with the car?
 

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Discussion Starter #6
Are you calculating MPG's by just reading the cluster display or are you tracking your miles driven divided by tank fill up's and taking an average? 6 MPG is very low even for city driving. No mechanical issues with the car?
I'm using the the calculator that comes with the car that shows you average speed/mpg. When driving I can actually watch the fuel needle drop substantially. I've used this this since I've had the car and there were no issues up until now. My visits to Sunoco are all too frequent compared to before. Thing is I'm not even goosing (foot to the floor) the vehicle. It's a beautiful G8 I get compliments on it all the time. Has never been run in the snow and rarely in the rain.
 

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i'd verify using actual math in gallons and your miles traveled first to rule that out. You should very easily notice 6mpg on your wallet though. You'd be burning through gas ~3x your normal rate.
 

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Have you checked the condition of the spark plugs?
 

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Discussion Starter #9
i'd verify using actual math in gallons and your miles traveled first to rule that out. You should very easily notice 6mpg on your wallet though. You'd be burning through gas ~3x your normal rate.
Thank you for responding Belo.

Like I said in my previous post, I can see the fuel needle dropping as I drive and my visits to Sunoco has increased tri-fold. I've had this car for way to long not to notice a huge change in mpg. It now eats up 3/4 of tank like its nothing. I did the mileage and from 3/4 of tank, usage miles was 47...ugh. No leaks, no codes coming up on my DBBII. When this started happening I thought someone or thing had punctured my gas tank so I looked under it after a fill ,a short run, let it sit for a minute and look under........Nothing! This is driving me carazy and my pocket too.
 

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Discussion Starter #12
Someone is siphoning your gas at night. I'd start with a security camera.
Already have cameras MGMGXP. It's when I'm driving not when getting into the vehicle and noticing fuel missing or low. It's already missing when I pull into the garage. :-(

Thanks for responding.
 

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Yes sir and defintitely worth a shot to take a gander.
 

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You're welcome. At the very least would inspect a spark plug from each side. Check the air filter and for vacuum leaks as well.
 

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Discussion Starter #16
You're welcome. At the very least would inspect a spark plug from each side. Check the air filter and for vacuum leaks as well.
Will do as per your instructions. The air filter doesn't even have 1,500 miles on it yet. I'll check for vacuum leaks, pass side plug, and driver side plug. If the plugs look funky what type do you suggest for my block? I had replaced the air filter with a high flow but it just created many issues so I reinstalled a new OEM type.

Thanks for taking the time to respond.
Ras
 

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Original equipment spark plug was 41-985 (iridium). It's replacement/equivalent appears to be 41-162.
 

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Discussion Starter #18
Original equipment spark plug was 41-985 (iridium). It's replacement/equivalent appears to be 41-162.
Thanks! Found the 41-985 & 41-162. Now the question is Pro or Platinum? I can look at what's there when pulled.

Thanks so much for your input. At 5.6 mpg my pockets wouldn't last long.
 

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Looking forward to see how this mystery gets resolved....subscribed.
 

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Professional or platinum?
 
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