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  #1  
Old 03-29-2016, 08:47 PM
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Bad gas mileage

Hello everyone, I have a 2007 Grand Cherokee with the 3.7L engine. Recently I have been getting terrible gas mileage. Right now it says im averaging only 10.2 MPG. In the past I think the best I have ever gotten was about 13 which I still think is below what it should be.

I have done a Tune-Up recently and replaced the plugs, Air Filter, PCV Valve. I Changed the Oil and also Run BG 44k fuel system cleaner every 6 months. What else can I do to increase my gas mileage?

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Old 03-29-2016, 08:48 PM
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Re: Bad gas mileage

Are you 4x4
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Old 03-29-2016, 11:23 PM
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Re: Bad gas mileage

Quote:
Originally Posted by jacobscottv View Post
Are you 4x4
Yes it is, but 10 Mpg? That has to be low even for 4x4
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Old 03-30-2016, 01:55 PM
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Re: Bad gas mileage

Quote:
Originally Posted by dvero1727 View Post
Hello everyone, I have a 2007 Grand Cherokee with the 3.7L engine. Recently I have been getting terrible gas mileage. Right now it says im averaging only 10.2 MPG. In the past I think the best I have ever gotten was about 13 which I still think is below what it should be.

I have done a Tune-Up recently and replaced the plugs, Air Filter, PCV Valve. I Changed the Oil and also Run BG 44k fuel system cleaner every 6 months. What else can I do to increase my gas mileage?
any codes you have something going on ? any kind of leak??
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  #5  
Old 03-30-2016, 02:42 PM
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Re: Bad gas mileage

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Originally Posted by dvero1727 View Post
Yes it is, but 10 Mpg? That has to be low even for 4x4
Yes it is, quite low! I have a couple of '98 Limited 5.9L V8 4x4's and at worst they average 12.5 or so. Usually around 14.

Have you tried logging miles and fill up gallons and calculating it the old fashioned way? I'm wondering if it might be one of the sensors used to calculate MPG... I used to have to keep a log for business expenses so got into the habit of doing that.

I would think with mileage that bad it you would notice other performance issues unless it's just the MPG display being wrong.
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Old 03-30-2016, 02:47 PM
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Re: Bad gas mileage

Quote:
Originally Posted by dvero1727 View Post
Hello everyone, I have a 2007 Grand Cherokee with the 3.7L engine. Recently I have been getting terrible gas mileage. Right now it says im averaging only 10.2 MPG. In the past I think the best I have ever gotten was about 13 which I still think is below what it should be.

I have done a Tune-Up recently and replaced the plugs, Air Filter, PCV Valve. I Changed the Oil and also Run BG 44k fuel system cleaner every 6 months. What else can I do to increase my gas mileage?
What was it before tune up??
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Old 03-30-2016, 03:25 PM
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Re: Bad gas mileage

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Originally Posted by dallas1 View Post
What was it before tune up??
Excellent point.

If it dropped after the tune up, worth rechecking/redoing that tune up.

If slow deteriorating, does the OPs state do smog checks where a clogged cat or similar could be dropping mileage?
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Old 03-30-2016, 03:31 PM
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Re: Bad gas mileage

I would check the O2 sensors with the help of a scanner with live data. Check if the 1-1 and 2-1 sensor voltage jumps up and down between 0.2V-0.8V. If they do , check the fuel trim figures (STFT and LTFT) These figures should stay at a single digit. If it goes well above the +10, then there is something wrong.
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Old 03-30-2016, 07:00 PM
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Re: Bad gas mileage

I think the best MPG I've ever had was about 12-14. I think before the tune up it was still around 12 or so. I'll have to check the O2 sensors. My TPMS light always comes on and has since I bought the jeep 2 years ago but my tires aren't low. I'm guessing it could be a bad sensor but that wouldn't be related to gas mileage would it?
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Old 04-02-2016, 10:02 AM
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Re: Bad gas mileage

No, TPMS problems should not have to do a thing with bad mpg, unless when you drive with low air pressure in the tires.
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Old 04-16-2016, 08:36 PM
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Re: Bad gas mileage

I currently have 3.7l (2006) 4x4. Average around city is 12.4 mpg. On highway with cruise it usually settles in at 18 on average.
Thays driving like a calm/ normal human being lol
In my 4.7, it would be about 11 in city and max of 17 highway.

Maybe try running some seafoam in fuel?

If you're gentle on gas pedal, you should notice a change.

Are you noticing any pullI'm either way? And burning smells?
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