11.2 mpg (us) :O

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moncalain

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Last September I bought a 2006 Libby Ltd, it has around 78k km (49k m) on it. Since I bought it I found it ******* gas. So before winter I change it to synthetic and I put a new air filter. This spring I put six new Bosh platinum +4, but I did not see much improvement. I also changed the tire to 245/70r16 BFG AT, they are a bit bigger but not that much... On my last tank I had an average of 11.2 mpg (US) or 21.61 L/100 with very normal driving, not hard at all. I know this is not normal but I don’t have any light or sign and I don’t know what to do to solve this problem??? :wtf2:
 

tjkj2002

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Somewhere between being sane and insane!
Put copper core plugs back in and put stock sized tires back on,mpg problem fixed.

Bosch plugs should never be used in anything and upsizing the tires with correcting the speedo and/or re-gearing will always give you worse mpg's.Those 245/70's may not be that much bigger on paper but in the big picture it's a huge difference between the stock sized tires,not to mention they weigh alot more also.


Or if your me you have a big grin on your face when your KJ get's 11mpg's as 10mpg's is the norm.
 

moncalain

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Lol tjkj2002! I think you have a big budget for gas... But for t he plug, I tried a set of new oe before changing it to bosh without better improvement, that's why I change them to bosh. And for the tire it is thru they are heavier, but with my winter tire (stock size) I have not a better mileage.
 

JeepJeepster

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Yeah you've got something going on there. Either you're idling a lot of driving the heck out of it. I get around 17mpg in the winter with my 245/70 tires.
 

moncalain

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No Idling and very normal driving JeepJeepster, and 11.2 is my best score to date, I've got worse, so i'm very far from 17... I know that there is a problem I just dont know what it is ??? If I dont find it soon I think I will change my Libby for something else, I just cant affort near $400 of gas per month!!!
 

LibertyFever

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I think something is wrong with your calculations moncalain or you engine needs the injectors cleaned. Myself I'm getting about 20 MPG on my 04 Liberty Sport. Let me explain the details.

I'm running ProComp LT245/75R16 AT tires and even though I have the BCM programed for the larger tires my speedo is off by as much as 10 kms/hr so I can't trust the odometer. I'm reading the MPG's off of my EVIC in the ceiling console.

The most accurate method of measuring your gas mileage must be with a GPS since we can't seem to trust our odometers.

Where do you live in Quebec moncalain? I'm in NB right next door. Last weekend we drove up to Perce Rock in the Gaspe.
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(this great view has been brought to you by Jeep)
 

rockymountain

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First if you have a GPS, see how accurate your speedo is. I have 245/75 tires and my speedo is only 1 MPH higher most of the time. I'm lifted and get 16.5 in the city right now.

My EVIC always shows 1 MPG higher than what I calculate meaning it is optimistic. If you are going by the EVIC it may be even worse.

You have to get the speedo programmed for your tires if you want any sort of accurate reading from the odometer. You said you don't get much better with your stock size winter tires, but you only use those in the winter right? Gas is different and will give you worse gas mileage in the winter, plus the cold temps make the engine run rich. So it may seem you are getting the same.

Now if everything is accurate then you have a major problem somewhere of course, but until then you need to make sure your instruments are calibrated.
 

moncalain

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Hi LibertyFever, I'm in the west in Abitibi-Témiscamingue. And for the calculaton, no nothing wrong with it, I check it with my evic and I do the calculation manually when I tank, it is always between 21 to 25 L/100 (11 to 9.5 MPG US). For most city driving and maybe 15-20% highway, and like I said, normal driving not hard at all. This is right that the tire are bigger and it can affect the speedometer, but mine is taller by just 0.4 inch, I dont think it can affect that much. And as I said to tjkj2002, I got about the same number with my winter tire.
 

rockymountain

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Hi LibertyFever, I'm in the west in Abitibi-Témiscamingue. And for the calculaton, no nothing wrong with it, I check it with my evic and I do the calculation manually when I tank, it is always between 21 to 25 L/100 (11 to 9.5 MPG US). For most city driving and maybe 15-20% highway, and like I said, normal driving not hard at all. This is right that the tire are bigger and it can affect the speedometer, but mine is taller by just 0.4 inch, I dont think it can affect that much. And as I said to tjkj2002, I got about the same number with my winter tire.

.4 of an inch will make a HUGE difference and plus they are heavier which will impact them even further. I explained why I think your snow tires don't seem to get much better mileage. You really have no idea how accurate your calculations are because you are basing them on something that is really unknown.

Just my thoughts.
 

CMCLEAN

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Around 11mpg in heavy stop start traffic in Haiti with a 3.7L. Clean filter, new plugs etc etc, but A/C running all the time. Glad it's not in the U.K., I'd need to sell a kidney !!
 

moncalain

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Thank you rockymountain, when I said that I have about the same number with my winter tire, I wasn't thinking about the winter month when the temperature is very cold and the long idling time this increase very much the number, no because your are right, you cant complain about a poor mpg in winter, every vehicle has bad mpg in winter... I was much referring to mars-april before I remove them.

I want to excuse myself to you all that are reading me, if you remark some error this is because I'm french and my english is not perfect!!! loll
 

moncalain

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This is the spec of the tire rockymountain, my 245/70r16 bfg are 29.5 inch 705 revs per miles and my stock tire are 235/65r17 29.1 inch 719 revs per miles.
 

tommudd

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Driving style and maintenance make a huge difference in the mileage of any vehicle
Since we don't know if you take off like a rocket ship and then slam on the brakes at every light or drive like Great Grandma its hard to say
Plugs, regular maintanace like changing all fluids, condition of brakes and mounting hardware , cleaniness of the throttle body, and many more things can affect mileage to some degree.
What all have you done so far besides changing plugs and air filter:shrug:
 

rockymountain

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This is the spec of the tire rockymountain, my 245/70r16 bfg are 29.5 inch 705 revs per miles and my stock tire are 235/65r17 29.1 inch 719 revs per miles.

I recant. So your tires really aren't worth mentioning.

It's a crap shoot then. hanging caliper, worn u-joints, clogged injectors, pcv valve, who knows.
 

moncalain

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Thank you tommudd, for my driving, like I said it is with normal driving, not like a rocket and not like a grandma... lol I fallow the traffic. For the maintenance I did one on the brake to grease the calliper pin and to check the pad, everything was fine there. I was wandering if some of you have tried the terraclean system to clean all the fuel system? If yes is it worth the cost, does it make any difference?
 

Akedos

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I can honestly say doing 65 rather than 72-3 on the highway saves me about 1 mpg. Other than that... copper plugs and stock tires. I get 19.5 mpg. Regular maint. Use A/C if you go over 35MPH. Windows down if you're going under that.
 

SabaII

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Kind of on topic, anyone use an at home fuel system and intake cleaner that is worth while? When I was in school on the gassers we had a canister that hooked right to the fuel rail and cleaned the injectors and that worked great. Anyone know of a system you can get in an auto parts place?
 

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