Gas Mileage

JustinC9905 · #1 03-05-2005, 11:34 PM

I just bought a 04 Wrangler in July. It seems that I am getting horrible gas milage...I am getting just about 14mpg for highway driving. I have the 4L, 3.11 Axel Ratio, and 30'' tires and it seems to be driving just fine. Is this a norm? and if not, any suggestions as to what might be wrong would be appriciated.

Dr. Eagle · #2 03-06-2005, 01:13 PM

That's very much the norm. I have an 00 Sahara with the 3 speed automatic.
You might try putting on a flowmaster, magnaflow, Gibson or Borla exhaust and especially a K&N air filter. It will help a smidge. Do you have a manual transmission? Is the vehicle broken in or brand new?

JustinC9905 · #3 03-06-2005, 01:35 PM

I have a manual transmission, and it has 3500 miles on it, mostly highway so I would consider it broken in.
I had a 94 Wrangler SE before this one, and I got much better gas milage with the smaller engine. I understand going with a bigger enginer causes you to lose some mgp, but I didnt expect it to be this bad.

JeeperRich · #4 03-08-2005, 06:01 PM

14mpg sounds low, unless you're a leadfoot.
When new, my '98 4L, 5spd got 18-20 around town, up to 22 highway (hardtop, 65mph cruise). Recently (95k miles) I'd get 16-17mpg highway (with mods), but drops to 9-10mpg cruising at 80-90mph.

JustinC9905 · #5 03-08-2005, 06:48 PM

I thought it sounded a little low to me. When I went back and checked my records I was getting like 17mpg back in July, and now it has steadily declined for the past few months...and the only thing that I have added is a roof rack, but I dont see how that would drop the milage by like 2-3 mpg. Anyone have any suggestions?

fredjacksonsan · #6 03-10-2005, 01:57 PM

O2 sensor will hurt your mileage, so you may want to have the dealer check it out under warranty.

Adding the roof rack will all a lot of wind resistance, so if you're doing 70 it'll eat some gas.

fredjacksonsan · #7 03-10-2005, 01:58 PM

Easy check for bad O2 sensor is the inside of exhaust is black and wet.

Had an '02 with hard top and 5spd, got 22-23 on highway also.

JustinC9905 · #8 03-10-2005, 05:16 PM

Yea see the problem is that I calculated the extra drag the rack causes and the additional horsepower that the Jeep has to use to overcome it ( thats what I get for being a mechanical engineer) and it really wasnt that much. I dont know what the problem is, but the gas milage is actually getting worse as time goes on. I took it into the Jeep people and they said that everything was fine...they tried giving me the reason its gotten worse is the type of gas during the winter.

fredjacksonsan · #9 03-10-2005, 07:06 PM

How's the inside of the exhaust?

JeeperRich · #10 03-10-2005, 07:12 PM

I doubt the "gas theory", and the roof rack shouldn't add that much more drag, but speed will (you know, square of velocity, right?). Between no top and hardtop, my mileage varied ~1-2mpg.
Check the O2 sensors yourself, make sure your air filter isn't clogged, then ask the dealer what is in the gas -- he's probably just trying to get rid of you by blowing smoke.

JustinC9905 · #11 03-10-2005, 08:26 PM

I will check the inside of the exhaust and see if its black. Also, I was wondering if anyone has had both a soft top and a hard top, and what if any difference they saw in their gas milage. Thanks for all your help.

fredjacksonsan · #12 03-11-2005, 07:50 AM

Quote:

Originally Posted by JustinC9905

I will check the inside of the exhaust and see if its black. Also, I was wondering if anyone has had both a soft top and a hard top, and what if any difference they saw in their gas milage. Thanks for all your help.

Black and wet

JustinC9905 · #13 03-12-2005, 02:12 PM

I checked the exhaust last night after driving it, and although it was black it did not seem wet. I didnt drive all that much, only like 5 or 10 minutes before I got to my destination, would that matter? Also, if there is anything else you can think of I would appriciate it. Thanks.

rad42 · #14 03-13-2005, 11:57 AM

As a former victim of a bad O2 sensor I would look at that pretty hard. My jeep seemed to be running perfectly but my mileage decreased as well and by the time I got it figured out my Cat was ruined because the truck was running so rich. the result......$$$$ gone! Good luck

Dr. Eagle · #15 03-14-2005, 12:39 AM

Quote:

Originally Posted by JeeperRich

14mpg sounds low, unless you're a leadfoot.
When new, my '98 4L, 5spd got 18-20 around town, up to 22 highway (hardtop, 65mph cruise). Recently (95k miles) I'd get 16-17mpg highway (with mods), but drops to 9-10mpg cruising at 80-90mph.

As I recall the EPA on mine with the automatic was 14/16. That is right about what I have been getting, although I have 32s on the vehicle.

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