Why am i getting such bad mpg - Jeep Wrangler Forum
Jeep Wrangler Forum

Go Back   Jeep Wrangler Forum > TJ Jeep Wrangler Forum > TJ General Discussion Forum

Join Wrangler Forum Today


Reply
 
Thread Tools

Please support our sponsors and let them know you heard about them on WranglerForum.com
Old 09-03-2012, 05:46 PM   #1
Jeeper
 
Join Date: Jun 2012
Posts: 121
Why am i getting such bad mpg

Hey i was wondering why i was getting such bad mpgs? Im getting around 10 mpg, i have a 02 with 4.0 and auto transmission. I have a 3.25 suspension lift with 33" tires, could it be that i only have 3.07 gears? I am getting close to 120,000 miles and the spark plugs i dont think have ever been changed. Im using 10w30 oil every 3000 miles and the air filter is clean. Any help to help me get better mpgs would be apreciated, and if your rig's set up is somewhat identical to mine tell me what your getting.

Bamafan4life is offline   Quote Quick Reply
Old 09-03-2012, 05:52 PM   #2
Jeeper
 
snowbrd84's Avatar
 
Join Date: Apr 2012
Location: Bethesda Maryland
Posts: 350
Write a letter to your congressman and hope that some day we quit mandating that corn be put in our gas. When that day comes, you will atleast see some improvement. Other than that, check your catalytic converter, it might be clogged.

__________________
"Why do it right when you can just do it!" Me
snowbrd84 is offline   Quote Quick Reply
Old 09-03-2012, 05:58 PM   #3
Jeeper
 
The-Judge's Avatar
 
Join Date: Sep 2012
Location: Arkansas
Posts: 145
I have a 02 wrangler with the 4.0 standard trans. I get between 14 and 15 MPG with 31 x 10.5 's.
The-Judge is offline   Quote Quick Reply
Old 09-03-2012, 05:59 PM   #4
Jeeper
 
orange05tj's Avatar
 
Join Date: Jun 2007
Location: Stop having a boring tuna. Stop having a boring life.
Posts: 3,897
Your driving a brick.
__________________
You'll be in a great mood all day because you'll be slapping all your troubles away.
orange05tj is offline   Quote Quick Reply
Old 09-03-2012, 06:27 PM   #5
Newb
 
finneyjr's Avatar
 
Join Date: Jun 2012
Location: Caddo Mills, Texas
Posts: 5
Quote:
Originally Posted by orange05tj
Your driving a brick.
I have a 04. I6, 5 speed & was getting 15 mpg on regular gas. I am on my second tank of no ethanol gas. First tank got 19.5 mph with no ethanol. With the cost per gallon more, it still drops operating cost from .25 cents per mile to .18 cents per mile.
finneyjr is offline   Quote Quick Reply
Old 09-03-2012, 06:30 PM   #6
Old School

WF Supporting Member
 
Water Dog's Avatar
 
Join Date: Mar 2011
Location: Roseville, CA
Posts: 3,973
Images: 11
If you are running 33" tires and haven't done a new speedo gear (or gear change), then you odometer is going to be off as well as your speedometer. That would account for "part" of your bad mileage (reading) problem. The other part (real mileage) would be the 33's with 3:07 dif gears. With that gearing you are not even close to being in your optimum power band.
Water Dog is online now   Quote Quick Reply
Old 09-03-2012, 06:32 PM   #7
Jeeper
 
Join Date: Dec 2011
Location: Chicopee
Posts: 115
try changing spark plugs you might get a little more, Check tire pressure. Air filter
sdptrey is offline   Quote Quick Reply
Old 09-03-2012, 07:19 PM   #8
Jeeper
 
Join Date: May 2011
Location: orange county ny
Posts: 46
Images: 3
120 ,000 on original plugs and you are worried about fuel economy ?
Change your plugs you will save the plug money in a tank of fuel.
you speedo is off 3 mil per gallon i bet and you are lousing 3 mils to the gallon with the lack of maintenance .
wellbuilt is offline   Quote Quick Reply
Old 09-03-2012, 08:05 PM   #9
Jeeper
 
Patrick H's Avatar
 
Join Date: Nov 2011
Location: Northern NM
Posts: 3,089
It doesn't make much sense to question poor fuel economy when you don't know the condition of your spark plugs.
Patrick H is offline   Quote Quick Reply
Old 09-03-2012, 08:38 PM   #10
Jeeper
 
shanes04wrangler's Avatar
 
Join Date: Feb 2012
Location: chicago
Posts: 274
change the plugs for a start, did mine at 120k when i bought my jeep and iam sure they were the originals and they were done for.
shanes04wrangler is offline   Quote Quick Reply
Old 09-03-2012, 08:40 PM   #11
Jeeper
 
mrcarcrazy's Avatar
 
Join Date: Jul 2009
Location: Midland/Odessa, TX
Posts: 3,385
do a basic tuneup. You, as noted earlier, are driving a brick. Adjust the lead content of the throttle foot.

10mpg is low, even for a brick...unless you drive like a 16 yr old.

Have you checked for trouble codes? (assuming the CEL isn't illuminated, and is functional)

If the Jeep has cruise, does it work?
__________________
I need another Jeep...
mrcarcrazy is offline   Quote Quick Reply
Old 09-03-2012, 08:45 PM   #12
Jeeper
 
shanes04wrangler's Avatar
 
Join Date: Feb 2012
Location: chicago
Posts: 274
yea 10mpg is bad, I have a heavy foot and i am getting around 14-16mpg 220-240mpg to the tank
shanes04wrangler is offline   Quote Quick Reply
Old 09-03-2012, 08:56 PM   #13
Jeeper
 
Join Date: Dec 2009
Posts: 174
MPG for 2.5L with automatic and A/C on all the time?

Have a stock '97 Sport 2.5L, with A/C, new rebuilt automatic transmission, hard top, +1" height suspension. 225/75-15 BRIDGESTONE DUELER A/T D695 tires at 35psi. Recent tune-up. It has been hotter then normal so I have been driving with the A/C on everyday. I have been averaging about 13 MPG in city bumper to bumper driving lately. I think I used to get over 15-16 MPG before the heatwave this summer? Is this normal for a 2.5L automatic with A/C on all the time?
autopc25 is offline   Quote Quick Reply
Old 09-03-2012, 09:24 PM   #14
Jeeper
 
bc3_Jeep's Avatar
 
Join Date: Nov 2010
Location: NE corner of Iowa
Posts: 1,543
May I suggest switching to a Prius????? My YJ 2.5 with 31s....no mods...AX5....ragtop...non-16 year old driving....60 mile commute daily....gets around 15mpg give or take.......corn content or not......corn IS NOT the problem.....nor is it the solution....... the solution is driving what you NEED instead of what you WANT....if you WANT mpgs.... you NEED a PRIUS........
__________________
"For Gawd's sake, put a RELAY in there or you could burn the whole damn Jeep to the ground" ...this quote brought to you by people who do not understand the law.....Kirchoff's, Ohm's, or Faraday's.
Violation of KISS shall always ring false in TRUE engineering. - ME___
Had 75CJ5, 89YJ, 93YJ. Have 82CJ7 & 95YJ____Not one burnt yet due to lack of relays.
bc3_Jeep is offline   Quote Quick Reply
Old 09-03-2012, 10:12 PM   #15
Jeeper
 
vertical horizons's Avatar
 
Join Date: Apr 2012
Location: Houston, Tx
Posts: 1,161
Quote:
Originally Posted by Water Dog View Post
... The other part (real mileage) would be the 33's with 3:07 dif gears. With that gearing you are not even close to being in your optimum power band.
Running 33's, what differential gears should he be running, to be at optimum power?
vertical horizons is online now   Quote Quick Reply
Old 09-03-2012, 10:14 PM   #16
Jeeper
 
vertical horizons's Avatar
 
Join Date: Apr 2012
Location: Houston, Tx
Posts: 1,161
Quote:
Originally Posted by snowbrd84 View Post
... check your catalytic converter, it might be clogged.
Other than taking the catalytic converter down, how do you check it to see if it's clogged?
vertical horizons is online now   Quote Quick Reply
Old 09-03-2012, 10:16 PM   #17
Jeeper
 
BrentR94's Avatar
 
Join Date: Jul 2012
Location: Grayslake, IL
Posts: 33
I was just having trouble with mpg with my 98 and I found out that the Catalytic Converter was clogged... I in clogged it and now it gets great mpg... Just a suggestion to look into.
Brent
BrentR94 is offline   Quote Quick Reply
Old 09-03-2012, 10:20 PM   #18
Jeeper
 
Join Date: Jun 2012
Posts: 121
Ive only been driving this jeep for about 6 months, my brother was the owner before me and i got to thinking that he never had the plugs changed, today was the first time i thought Of this, i guess ill go buy spark plugs and wires and get my 83 year old uncle to teach me before it gets to cold for him to get out. Im 17 and its time i learn lol
Bamafan4life is offline   Quote Quick Reply
Old 09-03-2012, 10:25 PM   #19
Jeeper
 
Join Date: Jun 2012
Posts: 121
Quote:
Originally Posted by bc3_Jeep View Post
May I suggest switching to a Prius????? My YJ 2.5 with 31s....no mods...AX5....ragtop...non-16 year old driving....60 mile commute daily....gets around 15mpg give or take.......corn content or not......corn IS NOT the problem.....nor is it the solution....... the solution is driving what you NEED instead of what you WANT....if you WANT mpgs.... you NEED a PRIUS........
I dont expect to get 30mpg, but 10 is horrible Id like to get atleast the 14-16 everybody else is getting, and im 17 but drive like im 71 im always atleast 5 miles below the speed limit and dont speed out ethier
Bamafan4life is offline   Quote Quick Reply
Old 09-03-2012, 11:05 PM   #20
Jeeper
 
SurfKaster's Avatar
 
Join Date: Mar 2010
Location: St. Augustine FL
Posts: 1,192
At a 120K there's a good chance your O2 sensors are original. I'd look into replacing your upstream sensors along with a new set of plugs to start.
SurfKaster is offline   Quote Quick Reply
Old 09-04-2012, 07:45 AM   #21
Jeeper
 
snowbrd84's Avatar
 
Join Date: Apr 2012
Location: Bethesda Maryland
Posts: 350
Quote:
Originally Posted by bc3_Jeep View Post
May I suggest switching to a Prius????? My YJ 2.5 with 31s....no mods...AX5....ragtop...non-16 year old driving....60 mile commute daily....gets around 15mpg give or take.......corn content or not......corn IS NOT the problem.....nor is it the solution....... the solution is driving what you NEED instead of what you WANT....if you WANT mpgs.... you NEED a PRIUS........
YOU ARE NOT ANSWERING ANY QUESTION.

And CORN IS THE PROBLEM. It contains 33% LESS energy content than pure gasoline and thus get significantly worse economy. Not to mention it damages engines that werent designed to run on it.

OP, go to this site and see if there is a station near you that sells 100% gas with 0% ethanol

pure-gas.org : ethanol-free gas stations
__________________
"Why do it right when you can just do it!" Me
snowbrd84 is offline   Quote Quick Reply
Old 09-04-2012, 08:06 AM   #22
Jeeper
 
vertical horizons's Avatar
 
Join Date: Apr 2012
Location: Houston, Tx
Posts: 1,161
Quote:
Originally Posted by snowbrd84 View Post
... go to this site and see if there is a station near you that sells 100% gas with 0% ethanol

pure-gas.org : ethanol-free gas stations
Very informative website.

However, I checked the website against where I live.
It amazes me that, even though Houston is so close to all those refineries, the closest "pure gas" gas station is 74 miles from my house.

And, according to the website, there is not one of those gas stations from Houston to Galveston.

Great website, though.
It'll come in handy when travelling.
vertical horizons is online now   Quote Quick Reply
Old 09-04-2012, 08:07 AM   #23
Jeeper
 
UnlimitedLJ04's Avatar
 
Join Date: Aug 2010
Posts: 6,889
did you recalibrate the speedo for the larger tires?
UnlimitedLJ04 is offline   Quote Quick Reply
Old 09-04-2012, 08:24 AM   #24
Jeeper
 
miketx's Avatar
 
Join Date: Oct 2011
Location: Allen, Texas
Posts: 109
If you are thinking about doing the plugs....and you suspect they have never been changed, you might as well do the cap/rotor/wires also. My Jeep had 99k miles on it when I got it. I did all these items and it ran better immediately. I didn't get a drastic bump in mpg, but it performed much better.
__________________
'98 Jeep TJ Sahara, 31s, 2" lift, SRC front/rear bumpers with carrier, KC Daylighters and driving lights
miketx is offline   Quote Quick Reply
Old 09-04-2012, 08:52 AM   #25
Jeeper
 
James249G's Avatar
 
Join Date: Jul 2011
Location: Greater Atlanta Area
Posts: 103
Quote:
Originally Posted by vertical horizons View Post
Other than taking the catalytic converter down, how do you check it to see if it's clogged?
X2... Anyone do a write up?
__________________
If you can't find it, grind it!
James249G is offline   Quote Quick Reply
Old 09-04-2012, 09:17 AM   #26
Knows a couple things...

WF Supporting Member
 
Jerry Bransford's Avatar
 
Join Date: Nov 2005
Location: Escondido, Calif.
Posts: 29,235
Images: 2
Quote:
Originally Posted by Bamafan4life View Post
Hey i was wondering why i was getting such bad mpgs? Im getting around 10 mpg, i have a 02 with 4.0 and auto transmission. I have a 3.25 suspension lift with 33" tires, could it be that i only have 3.07 gears? I am getting close to 120,000 miles and the spark plugs i dont think have ever been changed. Im using 10w30 oil every 3000 miles and the air filter is clean.
Yep your 3.07 gearing is causing your engine to run at too low of an RPM which is making it lug and run less efficiently.

Be wary on what spark plugs you install, 2000 and newer 4.0L engines are fussy about what spark plugs they run well on. Three good plugs for your 2002 include the Autolite APP985 (NOT the AP985), Champion 7034 (NOT the 3034), or Autolite XP985. The first two plugs are double-tipped platinums, the last one is iridium-tipped and the best of the three.

Quote:
Originally Posted by Water Dog View Post
If you are running 33" tires and haven't done a new speedo gear (or gear change), then you odometer is going to be off as well as your speedometer. That would account for "part" of your bad mileage (reading) problem. The other part (real mileage) would be the 33's with 3:07 dif gears. With that gearing you are not even close to being in your optimum power band.
X2 on all that. At least recalibrate your speedometer which takes five minutes to do with a new snap-in plastic speedometer gear which only takes a 1/2" wrench to instal. Your 33" tires are causing your speedometer to erroneously indicate you're driving slower and a shorter distance than you really are. Here's how...

http://www.jeepin.com/features/speedogear/index.asp

Quote:
Originally Posted by vertical horizons View Post
Running 33's, what differential gears should he be running, to be at optimum power?
For 33" tires and his 3-speed automatic, 4.10 is the optimal ratio.

Quote:
Originally Posted by Powder Monkey View Post
At a 120K there's a good chance your O2 sensors are original. I'd look into replacing your upstream sensors along with a new set of plugs to start.
Yes indeed on all points. When the 02 sensor goes bad, and they do go bad eventually, it usually erroneously indicates to the computer the air/fuel ratio is too lean so the computer then richens the ratio to the point it is full-rich and your mpg goes down the drain.
__________________
When you have a choice, buy American.

Jerry Bransford is online now   Quote Quick Reply
Old 09-04-2012, 01:22 PM   #27
Jeeper
 
pwroth58's Avatar
 
Join Date: Mar 2010
Posts: 65
Great info here! What is the optimal gear for the same setup only with the 5 speed manual transmission instead of the automatic?
pwroth58 is offline   Quote Quick Reply
Old 09-04-2012, 02:11 PM   #28
Knows a couple things...

WF Supporting Member
 
Jerry Bransford's Avatar
 
Join Date: Nov 2005
Location: Escondido, Calif.
Posts: 29,235
Images: 2
Quote:
Originally Posted by pwroth58 View Post
What is the optimal gear for the same setup only with the 5 speed manual transmission instead of the automatic?
4.56 for 33" tires when you have the 4.0L engine and 5-speed transmission.
__________________
When you have a choice, buy American.

Jerry Bransford is online now   Quote Quick Reply
Old 09-04-2012, 04:18 PM   #29
Jeeper
 
269jeep's Avatar
 
Join Date: Jun 2012
Location: Middle-O-Nowhereville Michigan
Posts: 169
Change those plugs!!! Then you might want to find out what gears you have.
269jeep is offline   Quote Quick Reply
Old 09-04-2012, 04:57 PM   #30
Jeeper
 
snowbrd84's Avatar
 
Join Date: Apr 2012
Location: Bethesda Maryland
Posts: 350
To determine what gears you have

Go for a drive on the highway, get up into your top gear and reach an RPM of about 2000 or more. Note the RPM and Speed. The speed needs to be the actual speed according to a GPS as your speedo may not be correct unless you have stock everything.

Then use this equation where Tire diameter is (inches), RPM is as displayed on your tach, and speed is in the actual mph according to a GPS.

Gear Ratio = [(RPM x 3.14 x Tire Diameter x 60) / (12*5280)] / Speed

__________________
"Why do it right when you can just do it!" Me
snowbrd84 is offline   Quote Quick Reply
Reply

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the Jeep Wrangler Forum forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.
User Name:
If you do not want to register, fill this field only and the name will be used as user name for your post.
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.



Thread Tools

Posting Rules
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off




» Network Links
»Jeep Parts
» Featured Product

All times are GMT -5. The time now is 11:57 AM.



Jeep®, Wrangler, Liberty, Wagoneer, Cherokee, and Grand Cherokee are copyrighted and trademarked to Chrysler Motors LLC.
Wranglerforum.com is not in any way associated with the Chrysler Motors LLC