Fuel Consumption

[kwmir]

Hi! I just bought a 2003 KJ Sport (3.7 L) and would like to find out from other folks out there what the ideal fuel consumption should be. My daily compute is approx. 35-40 miles. I have a stock KJ but my fuel efficiency is 13 miles per gallon. Second fill up it was 15 miles per gallon. I have seen on here that someone mentioned their KJ was giving mileage better than a Honda CRV. How can I improve my fuel efficiency? I also recently changed the air filter.

Please advise. Thanks in advance.

KM

 

[GoldBug]

My KJ is stock other than the 245/70R16 tires, just a tad wider and taller than the stock off road package size, and i've not gotten worse than 15 and no better than 20MPG. I have a the 6speed manual transmission which could explain the drastic differences. On a recent trip from WV to NC I made it from Elkins WV to Great Bridge VA (south of newport news) and got the 19MPG with a kayak on the roof and 2 bikes on a hitch rack. The only things i've changed is put a K&N Filter in her and have used mobile 1 synth oil since the first oil change. Some people on here say you're fuel economy gets better after the "break in period" but i haven't notice much difference.

 

[2003KJ]

First off welcome to the site.

I've also got a 03 KJ (as if my screen name didn't give that away). Right now i'm getting roughly 16-17 in the city, sometimes as high as 18-19, and about 20-21 on the highway...and I do alot of highway travel, especially on the weekends. All of this is with the a/c on 90% of the time.

Chances are your KJ needs a tune up, and bad. For some reason the plugs put in by the factory are wearing out alot quicker than an average plug should be given the set up. I replaced mine around 10K ago (25K on the odometer). When I looked at them, they looked as if I pulled them out of a vehicle with about 35-40K on it. I replaced them with Champions and noticed it ran a little smoother at idle, and the milage went up about 1mpg.

My next trick is I am only running BP regular in it. For some reason i'm getting excellent milage off of BP fuel. I've tried experiments with other name brands such as Exon, Shell, and Costco, and they've all yielded results of 14, 15.5, and 13.9 respectively, with the exact same driving habits.

I also try not to over-rev the engine. Anything above say 3000 rpm and you're really just making alot of noise. The KJ is one heavy vehicle and while the 3.7 is capeable of doing the task of hauling all that weight around, it certainly wouldn't hurt if the engine were a tad bit bigger. About 2500rpm's is as high as I go when accelerating in city traffic (getting on the highway is an exception obviously).

Try some of those tricks and see if your milage doesn't get better. You say it's about 35-40 miles. Is this highway miles, city miles, little bit of both?

Again welcome to the site and enjoy browsing around...i'm sure you'll find out alot of stuff about your newly acquired KJ that I'll bet you had no idea about. \/

 

[RIPGTP1997]

Eh don't feel bad, I'm seeing 13.5 in city and 18 on highway.....but it doesn't bother me.....I LOVE MY KJ

 

[jeepkj02]

Keep an eye on your tire pressure. Should be at 33psi, according to the Jeeps specs. I like to use Fuel Injector / Fuel System Cleaner. A performance muffler will help (ie, flowmaster, borla, etc..)

 

[kwmir]

Tire pressure

I was just going to look into that.I think my tires are running at 28psi or 29psi. Bringing the tire pressure up to 33psi might help some.

 

[2003KJ]

Ahhh yes I forgot to mention my tire pressure...i'm running 35psi of Nitrogen in all 4 of my tires....made a slight improvement over 33 in my case...so you might give it a try....28-29 is WAY to low.

 

[kwmir]

35psi?

Did you say you're running your KJ on Nitrogen at 35psi? Why nitrogen? I definately have to look into figuring out how to improve my fuel consumption. I envy folks who claim that their KJ gives better mileage than a CRV.

KM KJ

 

[cowdogg]

Re: 35psi?

. I envy folks who claim that their KJ gives better mileage than a CRV.

KM KJ

No one's Libby gets better mileage than a CRV PERIOD! Let's just let this rumor die right now, I'm tired or reading this. We bought the KJ's for reason's other than the mileage, or I would have bought a CRV. Your mileage is particularly low though, and I would suggest a major tuneup. Oil change, new spark plugs, PCV, air filter, ETC.... etc....

 

[AnthologyCT]

Mileage

As y'all know, I recently bought an '03 Libby

I'm averaging what I would say is about 17 in the city .................... BUT, when I run it on the highway, I'm averaging 25MPG.

Example: I just filled up my tank to the point where it was overflowing last week ................ I ran it dry to the point where the needle was on "E" for about 15 miles after the low fuel warning. .................. I had run it 420 miles during that fill-up. I'd say 90% of that was on the highway.

I haven't done JACK to it, except to fill the tire pressure to 35psi. And I only did that just to get rid of the tire squeek going around corners.

I just bought it with 40K miles on it 3 weeks ago .............. Check out my story: http://www.jeepkj.com/forums/viewtopic.php?t=4323

I bought it certified pre-owned .......... so I get the free service checks ............. all was well this weekend after my 40K service check. When I get my oil changed in another 2000 miles, I'll drop Mobil1 in it, and change to the KNP air filter.

Honestly, I think the best thing you can do is to CHANGE YOUR DRIVING HABITS. Before this, I had a Civic, and it was a high reving engine. I would floor it, then brake right before red lights in NY Metro City traffic .......... (like most Americans). I've since changed, as I cannot afford to do that anymore with this car.

Just doing that, you'll notice and appreciable difference. There is an optimal RMP range for this vehicle, that I would say is between 18,000 - 22,000 RPMs. If you keep it there on the highway, and your car is tuned properly .............. you should get excellent results.

 

[AnthologyCT]

Ni?

Ahhh yes I forgot to mention my tire pressure...i'm running 35psi of Nitrogen in all 4 of my tires....made a slight improvement over 33 in my case...so you might give it a try....28-29 is WAY to low.

Why Nitrogen? Nitrogen isn't that much lighter than air to notice an appreciable difference, is it? And where do you get Nitrogen?

 

[MoladoGuy]

Re: Ni?

Ahhh yes I forgot to mention my tire pressure...i'm running 35psi of Nitrogen in all 4 of my tires....made a slight improvement over 33 in my case...so you might give it a try....28-29 is WAY to low.

Why Nitrogen? Nitrogen isn't that much lighter than air to notice an appreciable difference, is it? And where do you get Nitrogen?

Nitrogen can be found at Belle Tire, Discount Tire, etc... Not sure of any gas stations that has a Nitrogen self serve.

 

[2003KJ]

Re: Ni?

Ahhh yes I forgot to mention my tire pressure...i'm running 35psi of Nitrogen in all 4 of my tires....made a slight improvement over 33 in my case...so you might give it a try....28-29 is WAY to low.

Why Nitrogen? Nitrogen isn't that much lighter than air to notice an appreciable difference, is it? And where do you get Nitrogen?

It's not so much lighter than air as it is more stable than air...I purchased my tires from Costco and had them install it and that's all they put in them is nitrogen...you just gotta request 35psi instead of the standard 33psi.

As far as I know there is no gas station or public airing place to get nitrogen....which is the downside if your tires do lose 1psi ro so. You might try asking your local tire guy if they carry nitrogen and would be willing to fill them up with that next time.

In the 6,000 mile intervals that I rotate and balance my tires, I've had to top them off with regular air (which can be added to nitrogen and still be safe) once. The only downside to adding air is sometimes it will throw them slightly off balance.

 

[yoda13]

When I had my Libby, and 03 Sport 4x4 automatic, I regularly saw mileage hover between 13-15 mpg in mixed driving. Switching to synthetic and a K&N filter drop in netted me another mpg or so. Straight highway driving got me 18-19 on rare occasions. These things, in their first year don't get as good of mileage as the later years do, and I am not even talking about the CRD. It is a great vehicle, it just doesn't get great mileage. Enjoy it \/

 

[JeepJeepster]

I get 15 in the city, thats normal for the libby. :-s I hope it doesnt get much worse with the bigger tires.

Nitrogen does not loose pressure as bad as regular air when it gets colder/hotter. I find myself adding and taking air from the tires almost every month due to this. The molecules of nitrogen are also bigger which in-turn doesnt leak out through the rubber like air will (Over time). O

 

[jeepkj02]

Re: 35psi?

. I envy folks who claim that their KJ gives better mileage than a CRV.

KM KJ

No one's Libby gets better mileage than a CRV PERIOD! Let's just let this rumor die right now, I'm tired or reading this. We bought the KJ's for reason's other than the mileage, or I would have bought a CRV. Your mileage is particularly low though, and I would suggest a major tuneup. Oil change, new spark plugs, PCV, air filter, ETC.... etc....

Unless it's a CRD!! \/

 

[hooperswish]

Synthetic too soon

I purchased my 06 3.7 libby two months ago. I changed the oil at 500 miles in order to get all of the break in crud out of my engine (As recommended by several on various web sights). I put in mobil1 synthetic. The problem is, I put it in too soon. The oil consumption went up, so I dumped it and put in Castrol GTX. I will put Mobil 1 back in at either my 3000 change, or the 6000 change. I think the engine needs a little more break in with standard oil.
My mileage has been around 17 in the city. I did a trip on Sunday up into the mountains, with a 12 mile 4x4 trip, and lots of twisting and turning over several mountain passes, although all highway with the 12 mile 4x4 exception. I got 22.47 miles to the gallon. I am psyched. The odometer now has 1200 miles, and I think my mileage will just get better. I do have the 6 speed manual, and it is a stock sport(No skid plates), but i also was loaded up with my family of four.
I have also researched that the K&N gives zero performance upgrade to the libby do to the fact that the stock system has all of the airflow it can use. Waste of money...In fact, it might hurt your engine do to oil from the filter being sucked in and letting in too much dirt. But that is just heresay, not first hand experience.
I LOVE MY LIBBY!!! \/

 

[MoladoGuy]

Re: Synthetic too soon

In fact, it might hurt your engine do to oil from the filter being sucked in and letting in too much dirt.

Tehee. (whistle)

 

[hooperswish]

Sorry Phil, I do not understand your reply "Tehee". Are you for or against K&N? I would like to get one myself if they are worth it.... :-k

 

[MoladoGuy]

Well I used the drop in K&N. You are not going to see some type of performance gain, but it does keep dirt out. You need to ensure that you keep it clean and not use too much oil.

Now I have a Cold Air Intake with a K&N filter. I just installed it over the weekend. I'm assuming I might see a slight increase in performance and possible gas mileage (1-2mpg?). Anywho it sounds sweet sucking in all that air and shooting it down the insulated air tube into the throttle body.

Also, you don't have to keep replacing your filter. Just keep it clean and oiled.