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Old 04-21-2011, 04:14 PM   #1
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reallly bad mpg in a stock jk

So lately my ECO meter has been saying im at about 11mpg. Granted I'm all city miles, I dont have a lead foot so I figured something smelled fishy. I've seen wranglers on 34's with at least 15 mpg.

So I conducted a test. I reset my ECO meter and drove down a straight road ON CRUISE CONTROL for about 5 miles at 35 mph. My ECO meter read 13 mpg.

On cruise control, down a straight road, at 35 mph... shouldn't I expect better then 13 mpg?

Then I hit a red light. 5 minutes sitting at the red light and my mpg dropped to 11.2 mpg. I understand I'm wasting gas sitting in one spot so my mpg would drop because I'm basically going 0 miles, but SO MUCH?! I was sitting at a red light!

I have a 2010 JK with 3500 miles. Is something fishy here, or is it just that I live in a college town with stop/go traffic at 35mph (at most) and parking garages every day?

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Old 04-21-2011, 04:18 PM   #2
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Sounds about right....

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Old 04-21-2011, 04:21 PM   #3
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That's lower than I'd expect too. I manually calculated my last tank on my four door at 18.6 mpg.

So . . . .

Have you changed your air filter or added an aftermarket air intake? If you've installed one of those oil-based ones, get it out of there. It'll clog and kill mileage.

Even assuming not, check your air filter anyway. If it got muddy while you were wheeling, you mileage could drop.

If all is well with the air filter, my first thought is to figure out if the problem is computer or mechanical. Manually track your mileage for the next tank or two and see if you're not doing better than that.
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Old 04-21-2011, 04:30 PM   #4
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I think you have a problem. My 2011 with 3.73 gears/automatic/33" tires gets a readout average that stays in the 18's. My 2007 with 4.10/automatic/32" tires averaged in the low 20's according to the dash readout.
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Old 04-21-2011, 04:41 PM   #5
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I would run a calculator test on a tank fillup. It could be the computer is not working correctly, not your Jeep's engine.
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Old 04-21-2011, 04:41 PM   #6
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I have not changed my air filter, I'm late for class so I'll check it later.

Maybe I'll take it into the dealer on Saturday. Its under warranty, so maybe this is a good time for me to take advantage of it.
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Old 04-21-2011, 04:43 PM   #7
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Do the math to see where you're at. If you're still at 11-13 mpg take it in.
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Old 04-21-2011, 06:19 PM   #8
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I'm getting about the same as you. Air filter isn't an issue, tire pressure is good, I've trouble shot about everything I can think of but can't find the culprit. I had a cracked exhaust manifold at one point. I was SURE this was the problem. Fixed it and it didn't make a difference. As much as I hate to say it, I've resolved to just excepting it. :shaking:
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Old 04-21-2011, 06:20 PM   #9
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Quote:
Originally Posted by redz1
I have not changed my air filter, I'm late for class so I'll check it later.

Maybe I'll take it into the dealer on Saturday. Its under warranty, so maybe this is a good time for me to take advantage of it.
If the dealer figures something out, will ya let me know?
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Old 04-21-2011, 06:28 PM   #10
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I'm getting 17.6 city with CAI and SuperChip and 22 on my 400 mile trip from NJ to OBX
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Old 04-21-2011, 06:53 PM   #11
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I averaged about 12 mpg this winter with a low of 11.2 mpg. that was around town and nothing over 5 miles.
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Old 04-21-2011, 07:04 PM   #12
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I average 18-18.5 (100% around town driving) in my 2010 2door (auto) per the eco readout. I have 17K on my JK.

In terms of statistics, driving 5 miles with cruise control does not tell the whole story...not reliable staistically.

Are your tires underinflated? do you (don't laugh, I see it all the time) drive with two feet?

If you are in severe traffic with constant stop and go, it can really bring down your mileage regardless of how gentle you are on the throttle.

At 3500 miles I hope it's not something mechanical - would not be a good sign. Keep us posted when you get it figured out!
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Old 04-21-2011, 07:26 PM   #13
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5 miles really isn't much data to base any frenzy of anxiety or angst upon.
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Old 04-21-2011, 07:32 PM   #14
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I get horrible mileage as well. One tank was almost entirely highway and I did finally hit 18mpg on the dash read out. Usually I'm hovering around the 14 range in city driving. I think it's the constant stop and go of a heavy, block shaped vehicle with mud tires. I tried varying rpm's (im a six speed). Try not to shift past 1500 rpms and didn't seem to be any significant improvement on one tank.

I will soon be changing all my fluids to synthetic (gear, transfer case, trans and engine) and am hoping to see some type of improvement. BTW, I only have 1400 miles on the clock so maybe it's not broken in yet.
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Old 04-21-2011, 09:44 PM   #15
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On thing that most people dont relize is its not so much how many RPS your turning but how much fule you are having to feed the motor to turn said RPM. you will burn less fuel turning 3500 when your are just giving it a bit of gas then you will turning 1500 with your foot halfway to the floor trying to speed up. thats why if you take jeeps that are the same in every way but gears and put them on a verry hilly road the one with the lower gears will get better milage if they are both drove at the same speed.
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Old 04-21-2011, 10:05 PM   #16
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Originally Posted by WatchThis! View Post
On thing that most people dont relize is its not so much how many RPS your turning but how much fule you are having to feed the motor to turn said RPM. you will burn less fuel turning 3500 when your are just giving it a bit of gas then you will turning 1500 with your foot halfway to the floor trying to speed up. thats why if you take jeeps that are the same in every way but gears and put them on a verry hilly road the one with the lower gears will get better milage if they are both drove at the same speed.


That makes ZERO sense to me. Revs are directly related to the work of the engine. The higher the revs, the more fuel you are feeding. If you have your foot buried and your only turning a steady 1500 rpms, something is wrong. Maybe I'm missing something in your post.
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Old 04-21-2011, 10:11 PM   #17
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Originally Posted by jk wrangler fan View Post
I get horrible mileage as well. One tank was almost entirely highway and I did finally hit 18mpg on the dash read out. Usually I'm hovering around the 14 range in city driving. I think it's the constant stop and go of a heavy, block shaped vehicle with mud tires. I tried varying rpm's (im a six speed). Try not to shift past 1500 rpms and didn't seem to be any significant improvement on one tank.
You don't have horrible gas mileage, you are getting what Jeep says you should be getting. 15mpg city/19 hwy.
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Old 04-21-2011, 10:41 PM   #18
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Originally Posted by Scooter_Trash



That makes ZERO sense to me. Revs are directly related to the work of the engine. The higher the revs, the more fuel you are feeding. If you have your foot buried and your only turning a steady 1500 rpms, something is wrong. Maybe I'm missing something in your post.
I think the idea is that for us with manual transmissions, you'll actually do better on MPG if you're in the power band and running efficiently rather than lugging. For example, if I shift too early and try to drive in 5th gear at 30 mph and 1200 RPM my mileage is actually worse than if I was in 3rd gear at the same speed but at 2200 RPM. That's why folks who are under geared with big tires often see an improvement in mpg when they regear. However, it's is a fine line--I definitely get my best mileage at low RPMs so SO LONG AS I'm not lugging.

At least, that's how I understand it.
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Old 04-21-2011, 11:35 PM   #19
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well put. Its all about the power band. I know 2 people who have goten better millage(be it in a chevy truck) by going from 3.73's to 4.10's. This dont make since to most people becouse the engine is turning more rpms but at the same time it is having to work less.
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Old 04-21-2011, 11:56 PM   #20
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Fuel economy sounds almost in the ball park - remember it's a Jeep!
For fuel efficiency buy a Prius! LOL!
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Old 04-22-2011, 01:06 AM   #21
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I get about 15mpg city, and about 17mpg hwy in my 2 dr JK Rubicon, manual...
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Old 04-22-2011, 03:27 AM   #22
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Originally Posted by 44Blues View Post
I average 18-18.5 (100% around town driving) in my 2010 2door (auto) per the eco readout. I have 17K on my JK.

In terms of statistics, driving 5 miles with cruise control does not tell the whole story...not reliable staistically.

Are your tires underinflated? do you (don't laugh, I see it all the time) drive with two feet?

If you are in severe traffic with constant stop and go, it can really bring down your mileage regardless of how gentle you are on the throttle.

At 3500 miles I hope it's not something mechanical - would not be a good sign. Keep us posted when you get it figured out!
Cruise control would usually give a high mpg. So I figured if I drove 5 miles on cruise control and got these results, it can't be any better driving normally for 100 miles... since I reset the ECO Meter, at that point in time driving in cruise control for 5 miles, my engine was burning 13mpg.

Tire pressure is fine, and I drive with my right foot

At the time I took the reading of 13mpg on cruise control, there was no traffic, I was cruising for that full 5 miles.
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Old 04-22-2011, 05:37 AM   #23
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well put. Its all about the power band. I know 2 people who have goten better millage(be it in a chevy truck) by going from 3.73's to 4.10's. This dont make since to most people becouse the engine is turning more rpms but at the same time it is having to work less.
Being in metric land its a bit hard to compare directly, but cruising at 100km/hr on flat highway with cruise control on, I got a slightly better readout of 10.1 litres/100km (23mpg) in 5th gear than I did in 6th gear at 10.5 litres/100km (22mpg) - (cruising for around 30 km then resetting the guage each time). This is a stock sport manual.

Around town we average around 12 to 13 L/100km (19 to 18 mpg)

Highway we average around the 10.5 L/100km (22mpg)

Highway best I have gotten was 8.8 l/100km (~28mpg) cruising at 80km/hr (~50mph)

If I were averaging 11 to 13 mpg (18 to 23 L/100km) I would definately be checking it by calculating distance per tank, if that confirms it then straight back to the dealer!!!
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Old 04-22-2011, 04:34 PM   #24
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i just drove from Pittsburgh to Clearwater and averaged around the 10.8 L/100km roughly 22/23 MPG

manual tranny
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Old 04-22-2011, 04:48 PM   #25
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I would definitely calculate the mileage at the pump. I never trust the computer stuff related to fuel mileage or miles left to empty. There are times I have gotten my wifes display in her car (a mazda) to show 47 mpg...YA RIGHT! Test it at the pump...that will give you the most accurate mileage that you are getting.
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Old 05-02-2011, 11:52 AM   #26
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Just an update...

I'm driving home 7 hours south for the summer..

2 Hours on the highway so far, going 70 on cruise control the whole way... My eco meter is reading 16.8

Still seems low for highway on cruise control am I right??

I checked tire pressure and all the goods before I left. Everything is normal.
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Old 05-02-2011, 12:11 PM   #27
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Just an update...

I'm driving home 7 hours south for the summer..

2 Hours on the highway so far, going 70 on cruise control the whole way... My eco meter is reading 16.8

Still seems low for highway on cruise control am I right??

I checked tire pressure and all the goods before I left. Everything is normal.
Seems a little low...but I would still check it at the pump
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Old 05-02-2011, 12:22 PM   #28
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In the original post, 34s were mentioned. Has the speedo has been recalibrated for that? Before getting into more complex reasons confirmation of that I thought would be a good idea. Otherwise the computer sees less miles driven but all the fuel being used for the real miles... giving poor apparent but not real MPG. Agressively treaded tires will suck mileage down also.

An average over several hundred miles would be much more accurate also, since that effectively dilutes the stoplight idle poor mileage out.
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Old 05-02-2011, 12:34 PM   #29
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I'm on stock 32s. I was simply saying I've seen people with 34s get better mpg then me.
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Old 05-02-2011, 12:54 PM   #30
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I'm on stock 32s. I was simply saying I've seen people with 34s get better mpg then me.
Just checking but you didn't change to 32's right? They came on the Jeep when it was new?

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