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Unread 07-08-2012, 09:19 AM   #1
cactus_jack
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Horrible Mileage

I'm getting about 18mpg in my 08 Compass. I've done a full tune up, reset the ecu, everything I can think of. Any clue as to what the heck is going on? I'm leaving for florida in a week and would like some good mileage!

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Unread 07-08-2012, 09:35 AM   #2
FujativeOCR
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I wish my 2011 Patriot got 18 mpg.
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Unread 07-08-2012, 10:43 AM   #3
cactus_jack
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I used to get around 25mpg but now its like it fell flat on its face
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Unread 07-08-2012, 11:27 AM   #4
bigkat91
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Tire pressure? Do you have a sticky caliper??
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Unread 07-08-2012, 12:28 PM   #5
cactus_jack
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Tire pressure is fine, just did the brakes about 3 or 4 months ago, no sticky caliper. Rolls freely
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Unread 07-09-2012, 07:21 AM   #6
IRSmart
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are we talking mostly city or highway? what is your drivetrain setup? i notice in my CVT-I 4WD in the city i'll get 18-19 but that's because i constantly floor it to merge with all the on-ramps around here, so it kills my mileage. i got 29 on the highway last year during a trip.
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Unread 07-09-2012, 09:24 AM   #7
cactus_jack
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Mostly highway. It gets even worse in city driving
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Unread 07-09-2012, 09:48 AM   #8
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Jack the same thing happened to mine on the first tuneup @ about 39K, no explanation for it at all!! I was during a long trip with different gas stations so bad gas wasn't considered a factor. I had to do the battery disconnect about a half dozen times for it to really take effect and stay where it should be.
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Unread 07-09-2012, 12:09 PM   #9
cactus_jack
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Quote:
Originally Posted by Gramps View Post
Jack the same thing happened to mine on the first tuneup @ about 39K, no explanation for it at all!! I was during a long trip with different gas stations so bad gas wasn't considered a factor. I had to do the battery disconnect about a half dozen times for it to really take effect and stay where it should be.
I was wondering when you'd chime in, Gramps

I'll do several resets and see if thats the problem. I'm pushing 80k on mine now.
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Unread 07-09-2012, 07:26 PM   #10
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Cactus_jack let us know how that works out. similarly i have an 08 pat, 70,000 miles and i never have been able to replicate the mileage i got out of her in say the first 20-30k after i drove her off the lot new. tire pressure is on non-issue, though at one point i had a sticky left rear caliper, dealer said at one point the caliper may have locked then worked itself loose again. even after they repaired it i cant say my mileage got any better
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Unread 07-10-2012, 09:35 AM   #11
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That's about the same mileage as me, 80K. I'm down to about 22 mpg right now but I'm not driving much lately. Just short <2 mile trips in town. It was very frustrating and the dealer chalked it up to bad gas at about 10 different stations?. WTH? What was interesting about it was that while I was on the freeway (after doing a reset) I could watch the mileage drop off .1mpg about every 10 - 20 miles or so.

It only took me a day to chime in. Now that I'm officially retired I have many more 'other duties as assigned' from the high command and mil. Oy vey!
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Unread 07-10-2012, 12:20 PM   #12
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Ive had highway miles vary from 18-24 mpg on the same exact stretch of flat highway (fresno to sacramento) before. In the end I chalked it up to having a headwind going one way and a tailwind going the other.
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Unread 07-10-2012, 02:34 PM   #13
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Quote:
Originally Posted by cactus_jack View Post
I'm getting about 18mpg in my 08 Compass. I've done a full tune up, reset the ecu, everything I can think of. Any clue as to what the heck is going on? I'm leaving for florida in a week and would like some good mileage!
1st what plugs where used? That can make a huge difference,if not OE plugs all bets are off for mpg's,those fancy plugs often reduce performance and mpg's.

Also resetting the ECU will have a negitive effect on mpg's.Your computer is a learning computer which does learn your driving patterns after a few weeks.Resetting the RAM in the computer erases what's it learned so it goes back to default settings,which are richer which means less mpg's,till it relearns your driving habits.
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Unread 07-10-2012, 02:37 PM   #14
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Quote:
Originally Posted by FujativeOCR
Ive had highway miles vary from 18-24 mpg on the same exact stretch of flat highway (fresno to sacramento) before. In the end I chalked it up to having a headwind going one way and a tailwind going the other.
What grade fuel are you using regular or mid grade? Curious of that would make a difference ? Might land a deal on a compass today unless fiancÚ wants to $pend on wrangler
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Unread 07-10-2012, 02:53 PM   #15
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Quote:
Originally Posted by tjkj2002 View Post
1st what plugs where used? That can make a huge difference,if not OE plugs all bets are off for mpg's,those fancy plugs often reduce performance and mpg's.

Also resetting the ECU will have a negitive effect on mpg's.Your computer is a learning computer which does learn your driving patterns after a few weeks.Resetting the RAM in the computer erases what's it learned so it goes back to default settings,which are richer which means less mpg's,till it relearns your driving habits.
That may be 'buy the book' but reality has proven different on too many occasions. I only used a 'better grade of plug, nothing fancy or even worth remembering. Every time you go to work on anything electrical it says 'Disconnect the battery' so nothing out of the ordinary is being done here, just SOP.

FYI: I have never used anything other than regular gas and that's hard to find with out the 10% ethanol.

Here is a link to some of the spark plugs that we have tried. http://www.jeepforum.com/forum/f98/n...-plugs-567229/
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