[sfdl32]

Ok folks I've had my '05 unlimited rubicon for almost two years and was hoping my fuel mileage might improve but instead has gotten worse. The jeep is completely stock except for a swing away tire carrier, warn m8000 winch on warn winch plate, and a K&N airfilter. I'm currently getting 13-14mpg around town and only about 14-15 mpg freeway. The jeep has 30,000 miles now and I'm due to change spark plugs and axle gear lube. I'm running a soft top with stock tires and rims with no lift and it's the six speed tranny. Any suggestions as what I can do to improve fuel economy? I'm looking at putting a 4" lift on it soon and don't want to loose any more mpg than I have right now.

[98tjwrangler]

Number one, fuel mileage will almost never get better with age. Number two, you drive a Jeep, MPG is gonna suck. And number three, your not going to get much better mileage no matter what you but here are a few pointers. Make sure your tires are properly aired up at all times. It helps to have nitrogen put in them. The air pressure stays stable longer. Plugs and wires help a little. Go with a bigger plug wire for better spark. Exhaust mods cat back or other wise will help slightly. The K&N air filter you have is about the best you can do unless you put an intake on it. Also try driving your vehicle a little easier. Shift gears at a lower RPM, don't come to a full stop unless absolutly nessasary, coast down hills ect.

[Sccafire]

Don't worry about replacing the plug wires you do not have any. You have whats called a DIS (Distributorless Ignition System.) The gas mileage you stated sounds about right. Just remember a box on wheels will not get good gas mileage.

[asjeep]

Yep you drive something with all the aerodynamics of a brick...... I did find that a hardtop seems to increase mileage on my tj, despite the extra weight.... I think it provides a smoother surface... but who knows....

My personal bet.... your pushing that skinny pedal too much ... we all do it

[sfdl32]

I appreciate the comments, but I'm not new to jeeps or vehicles in general. I'm keeping the tires properly inflated, I know I don't have plug wires and it's got DIS with coil packs and I drive very easily, hardly use brakes they usually rust more before they actually wear out. I had almost the same engine in my '88 wrangler that I swapped from a 2000 cherokee with a nv3550 tranny, same 4.10 gearing and 7" lift with 33 or 36" tires depending on what I was doing and I averaged 16mpg around town with 21mpg on the freeway at 65mph. So I guess it's just the added weight of the LJ body that's causing the issue. Just thought maybe there was something I could do about it that I hadn't already thought of. Thanks for all the replys so far guys.

[Unlimited04]

Originally Posted by sfdl32

Ok folks I've had my '05 unlimited rubicon for almost two years and was hoping my fuel mileage might improve but instead has gotten worse. The jeep is completely stock except for a swing away tire carrier, warn m8000 winch on warn winch plate, and a K&N airfilter. I'm currently getting 13-14mpg around town and only about 14-15 mpg freeway. The jeep has 30,000 miles now and I'm due to change spark plugs and axle gear lube. I'm running a soft top with stock tires and rims with no lift and it's the six speed tranny. Any suggestions as what I can do to improve fuel economy? I'm looking at putting a 4" lift on it soon and don't want to loose any more mpg than I have right now.

I've got a 2004 LJ setup a lot heavier than yours and i'll tell you what your problem is.

Get hold of that K&N CAI or air filter or whatever you have, remove it from the jeep and throw into the nearest trash can. You wasted your money with that thing....they are the biggest piece of crap air filter for jeeps EVER. the oil attracts LOTS AND LOTS of dust, dirt, debris and other junk that clogs your filter, causes a high, rough idle and BAD MILEAGE. they don't have a high flow rate, they get clogged very quickly, and they require $20-30 dollar maintanence kits. see jerry's comments here.

I'll bet if you replace your K&N filter with a Wix or AC Delco paper air filter, you'll be back up to 17-18 mpg hwy. See the COLD AIR INTAKE TECH THREAD linked in my sig. I used to run a similar setup and documented my observations here. I've got almost 52k on my LJ, and I get 15-19 mpg, depnding how heavy my foot is.

[gamble71]

Our stock LJ only gets 14-15. If you're getting that with all the mods you've listed (winch/tire carrier), you're doing something right.

[Unlimited04]

Originally Posted by gamble71

Our stock LJ only gets 14-15. If you're getting that with all the mods you've listed (winch/tire carrier), you're doing something right.

i can easily get 14-15 hwy if I drive like most people drive. to get 18mpg or even 20mpg, you gotta drive like grandma. Never go over 2000rpms, never leave 55-60mph in OD, coast in every opportunity and use the OD OFF button below 50mph. I get BETTER mileage in 3rd at 45mph than in OD at 45mph because the damn engine is lugging so bad because of the stupid 42RLE. if you have a 6-speed, you can get 21-22mpg if you know how to drive it. as soon as you go 70mph, your mileage will drop to 15mpg on a good day.

[mdm]

Originally Posted by 98tjwrangler

...Make sure your tires are properly aired up at all times. It helps to have nitrogen put in them. The air pressure stays stable longer. Plugs and wires help a little...

Unless he is using a CO2 bottle to air up his tires he is already running 78% nitrogen. That's all that is necessary unless you are operating a space shuttle, 747, or a Formula One car. Running 100% nitrogen in your tires is a waste of time and money but it does make for good internet gossip.

[NaeKid]

I also have an LJ. I find that winter driving at -20°C (-4°F) the fluids in my Jeep freeze up and the engine needs to work alot harder just to move the Jeep (in any gear). When the temperature reaches 0°C (32°F) my gas milage improves significantly.

I installed an Autel MaxiTrip auto-computer into my Jeep so that I can see exactly what is really happening in the engine - temperatures and such. It has been quite enlightening knowing what the air-temperature is at the AI (air-intake) vs. the outside air-temperature vs. WT (water temperature) .. and what the engine-load really is (towing, empty, idle, etc) and what the real-time fuel-economy is.

I have installed the Airaid throttle-body spacer and I noticed that my milage is better - especially when the outside temperature is greater than 10°C (50°F) but less than 30°C (86°F). The Airaid seems to work best at a static-RPM of between 2,000 and 2,300. I have rarely had my Jeep upto 3,000 RPM, so I don't know how well the Airaid works at the higher RPM's.

I have only had my MaxiTrip in my Jeep for ~3 months, but, I am using the "black-box" technology built into it so that I can compare different sets of readings based on the averages of the temperature of the month.

[jinx44]

Originally Posted by mdm

Running 100% nitrogen in your tires is a waste of time and money but it does make for good internet gossip.

And a good gimmick for the tire shops.

[asjeep]

were not trying to get on you (at least i'm not ), it just seems that these posts are usually someone looking for some miracle... think browns gas, spacers, chips, etc etc etc..... only true way to get better mileage is the stuff your doing, maintaining your vehicle, driving well, etc...... course it does help if you can get a good tailwind everywhere you drive

[jr1966]

I don't think there is anything much to do with the bad mpg of a Jeep, specially an LJ. Since you plan on putting a 4" lift, I would assume that would include larger (and heavier tires). It's just gonna get worse. The biggest drop in mpg I've encountered in my LJ is when I switched from 31s to 32x12.5 on my 8" Ravines. Now, in order to get a good contact patch with the 12.5" wide tires and 8" wide rims, I had to air it down to 25psi. The result of huge rolling resistance due to lower tire pressure plus larger & heavier tires resulted in at least a 6mpg drop minimum in my city mileage. It's just unbelievable. My LR3 and 7-series used to be the thirstiest in my fleet. Now, it's my LJ.

[UnlimitedNJ]

I get a combined 14-15mpg. 33's, 4.56's, 6 speed and 110k miles. My LJ is a pig too (corners, rockers, tire carrier, tummy tucker, and every other skid known to man). So while 14 isn't too terrible for you, it will only get worse with skids and bigger meats.

[Strizzy]

I was getting some REALLY bag MPGs the last month or so. I replaced my plugs end of November and was averaging about 17-18 until around mid January I dropped to about 9-10. No codes popped up. i tried different brands of fuel, new air filter, adjusting tire pressure, etc. I borrowed a scan tool from work which can display real-time info from all the sensors while driving. Ended up my 2/1 O2 sensor was erratic and giving readings all over the place, but still within its spec range, so it wasn't tripping the CEL. After replacing both O2 sensors (I like replacing them in pairs), it seems that everything is back to normal.
BTW, I have just under 48k on the clock.