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Unread 01-11-2009, 10:58 AM   #1
Yankee802
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Very poor fuel economy!

I just got my Jeep, and I'm only getting around 14mpg. Before buying one, I did research and most were averaging about 19mpg, and some 24mpg on the highway! What could cause me to get such bad fuel economy? I put in 93 octane, the plugs have been replaced recently, oil changes regularly, what else can I do to improve this?! (and I drive conservativly, I save my heavy foot for my BMW)

Geoff

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Unread 01-11-2009, 11:00 AM   #2
xJoshxx
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93 octane ur wasting your money honestly does nothing for you unless it's been reprogramed too

and what size motor Inline 6 or V8 the 4.7V8 isnt known to get 19 at all...

change ur o2 sensors that can help alot fuel filter also!
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Unread 01-11-2009, 11:06 AM   #3
DothanJeep
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for my jeep, I find the CHEAPEST gas out there, no need for 93.
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Unread 01-11-2009, 11:29 AM   #4
cmonson
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93 oct if not required may actually be damaging your engine. Only reason to run higher than 87 is if you have a 4.7HO engine.

I have no idea why people have this mis-belief that 93oct gasoline is better.
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Unread 01-11-2009, 11:41 AM   #5
windsors03cobra
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Quote:
Originally Posted by cmonson View Post
93 oct if not required may actually be damaging your engine. Only reason to run higher than 87 is if you have a 4.7HO engine.

I have no idea why people have this mis-belief that 93oct gasoline is better.
Damage ? C'mon.

93 Octane is better for resisting detonation it also has a better additive package than low test.

Being that the OP's truck is a 04 overland I gotta thinks its the V8 in which case that mileage sounds about right. My doggy 4.0 gets the same mileage as well as my V8 Ford SUV. Nice rides tho very comfy and snow-going.
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Unread 01-11-2009, 11:42 AM   #6
subliminal
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If you have a V8 then thats about what you can expect with the winter blend gasoline. I have the 5.2 and get about 12.8 in the city.
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Unread 01-11-2009, 11:44 AM   #7
rm2001wj
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Unfortunately, you are learning that mpg threads are full of notoriously inaccurate claims. The EPA estimates are pretty close to what you can expect. My wife's 04 (purchased new) mpg has usually been between 14 and 15 mpg for city driving. EPA estimates for 04 4.7L is 15 city and 20 highway.

My 01 (before and after supercharging) gets similar mpg.
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Unread 01-11-2009, 12:09 PM   #8
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Quote:
Originally Posted by subliminal View Post
If you have a V8 then thats about what you can expect with the winter blend gasoline. I have the 5.2 and get about 12.8 in the city.
I am only getting 9.6 in the city...but I drift alot too.
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Unread 01-11-2009, 12:39 PM   #9
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Guys, he has an Overland so it's a 4.7HO, which requires 91. I've actually get nearly 2mpg better on the hwy (18.1 vs 16.2 avg) if I put 89 in my 5.2 ZJ versus 87 (Shell).

To the OP: are there larger tires than stock, any performance mods or accessories, alignment issues, lift, etc. that may play a role here? I wouldn't think you could get much more out of it though even if it was stock and running tip top, maybe 18-19 hwy?

Changing diff fliuds and checking your brakes over to make sure your calipers or parking brake aren't sticking slightly is also something to check. Tire pressure and timing traffic lights or stop signs are also variables in fuel economy but I highly doubt you will get over 20mpg with a 4.7HO regardless of what you do.
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Unread 01-11-2009, 01:22 PM   #10
Yankee802
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Eldorado: Everything is stock, tires show 35psi, door jam shows they should be 33, can't believe 2 pounds would make a big difference. I will try that Jeep fuel additive I read about, might replace my o2 sensor and fuel filter. But like you said, it might not make a difference.

Because I am getting noise when turning left, I believe my viscouse coupler needs to be replaced, so I was thinking of just swapping the TC for a 242. Do you guys think running in 2wd will help? Gas is on the rise again, every little bit helps.

Geoff
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Unread 01-11-2009, 01:32 PM   #11
rm2001wj
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Quote:
Originally Posted by Eldoradoman View Post
Guys, he has an Overland so it's a 4.7HO, which requires 91.
........
Actually, the 4.7 HO only requires 87 octane (lower octane works at higher elevations). Using higher octane enables it to make more power than it would with 87. This is not a general claim that higher octane produces more power. Instead, the HO PCM using knock sensor input retards the timing so that it runs very well on 87. The consequence of this "detuning" is that the engine makes less power. The power loss is not noticeable under normal conditions (and has little effect on mileage). It's when operating under wide open throttle conditions that the power loss can be noticed.
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Unread 01-11-2009, 01:45 PM   #12
gatorayde
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It's a jeep, buy a honda if you want good gas mileage.
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Unread 01-11-2009, 01:56 PM   #13
Haleyrz
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do this in order...
Check tire pressure (you said the door says 33psi, so air them down to that)
check and change air filter if needed
Do full tune up including changing fuel filter
Sea Foam your Jeep or use Mopar equivilent
Use lower octane gas like said above
if all else fails, take it to a shop and get the injectors cleaned. Outboard cleaning perfered, but onboard cleaning will do fine.

I drive a 1996 JGC 5.2L V8 and I average about 15 city and 20 highway. Got about the same when I bought it, but then it dropped to an average of 10 mpg, went and got the injectors cleaned and that solved everything. Also remember winter gas. Right now I'm getting about 10 city and 15 highway because of the winter mixture gas. Not sure what its like over in virginia beach, but that may have something to do with it. You definately should at least be getting a little more than you are.
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Unread 01-11-2009, 01:57 PM   #14
Eldoradoman
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Quote:
Originally Posted by rm2001wj View Post
Actually, the 4.7 HO only requires 87 octane (lower octane works at higher elevations). Using higher octane enables it to make more power than it would with 87. This is not a general claim that higher octane produces more power. Instead, the HO PCM using knock sensor input retards the timing so that it runs very well on 87. The consequence of this "detuning" is that the engine makes less power. The power loss is not noticeable under normal conditions (and has little effect on mileage). It's when operating under wide open throttle conditions that the power loss can be noticed.
My bad, I guess it's only 'recommended' that 91 be used then.

OP: Running in 2WD mode will produced negligible results, most seem to get 0.5mpg or less by doing this. Check the fluid level in the transfer case too.
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Unread 01-11-2009, 04:40 PM   #15
cmonson
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Quote:
Damage ? C'mon.

93 Octane is better for resisting detonation it also has a better additive package than low test.
Premium Gasoline
Certain high performance engines benefit from use of high octane fuel. For other engines, using a fuel with a higher octane rating than the vehicle requires sends unburned fuel into the emissions system and catalytic converter. This puts unecessary stress on the emissions system. For some vehicles, a rotten egg smell coming from the tailpipe signals use of too-high octane gas.

from here: http://chemistry.about.com/library/w...abyb100401.htm

using too high of octane is going to do more damage than good...

if you have the 4.7HO, use 91oct. This is a higher compression engine, and probably will run best with 91 even with the knock sensors to adjust the timing.
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