What mpg is everyone getting w/an auto xj?

[yenkoz]

I have a stock 90 4.0/AW4 4WD (90k miles) with 235/75/15 tires and average 20mpg on 50% highway/50% city, or 100% highway. I recently threw in some of the new bosch 4 hole fuel injectors to see if it would bump it at all.

 

[djlarroc]

When was the last tune up done? Any mechanical issues at all? Mine ran well enough, but when I pulled the plugs, cap, and rotor, I was surprised it ran at all. Tuneup and a few simple things gained 3mpg when my junk was still basically stock. But, this fall, my mileage has tanked again. Not sure if it's the winter gas and my driving, or if I've got a sensor or mechanical problem that I haven't been able to find.

All that being said, 15mpg for mainly city driving isn't bad. Your friends may claim 20+ in the city, but I'd be very skeptical of those claims.

To be honest, not sure when last tune was done. But you are right, might as well do that investment before I convict my jeep anymore haha. If I could gain another 3 mpg w/a tune, I'D BE STOKED! Still, jealous of my brother's jeep getting that w/31s on 3:07 though.

Not sure what % of city/hwy my friend got on that mileage. My bro's is about 50/50 though.

I average about 16mpg in a stock 2000, LT235/75 R15 tires, with mixed driving. I get about 14 in town and 19 highway. My average seems to be in line with the other XJs on fuelly.com.

Thanks for that link. I signed up. Interested to see how it compares.

To the OP for 70% city driving this may be what it'll do. A lot of stop and go, idling can kill MPG real quick.

Forgot to say we run 235 tires
I would check GPS to see if the Speedo/odometer is accurate.

Doing a tune up would probably be best since it is new to you.

I don't know about the 97s but the older XJ had a upgrade in swapping out the injectors with ford injectors, I don't know if it actually improve millage (as some ebay sellers claim), I did ours years ago because the factory injectors seemed tired....

Noted. I will check the speedo next time. I don't have a GPS tho. How else can I check it? I've also read of the 703 injectors. Might try that if the tune doesn't help. My drive is pretty bad stop and go the whole time. Rush hour driving twice a day.

I have a stock 90 4.0/AW4 4WD (90k miles) with 235/75/15 tires and average 20mpg on 50% highway/50% city, or 100% highway. I recently threw in some of the new bosch 4 hole fuel injectors to see if it would bump it at all.

So your jeep got the same mpg 50/50 and 100% hwy?

 

[djlarroc]

Forgot to mention, I have another friend w/a '97 auto 4.0 on 31s and he says he's getting 11 mpg. Stock 3:55s. Recent tune and 02 sensor.

 

[TRCM]

My 88 with a BB and 31's, stock 3.55 gears, gets ~ 14 mpg (it does have over 350k miles on it tho) since I installed a TCC lockup switch.

My 96 with a 3" lift and stock gears/tires get 21-22 mpg

Now, both get ~ 12 mpg when driving to and from work, but that's mainly because my commute is so short, the engine never really warms up. (~ 2 miles 1 way).

I get about 200-225 miles on a tank driving to and from work in the 96, but on the highway, I get 400-425 per tank.

Check your speedo with a GPS. I found out when I was testing the TCC lockup switch, that my stock speedo is WAY off. I mean with 31's, the speedo should have been off by ~ 14%, but it was only off by 9%, so my stock speedo was off by 5% at least.

You can also time how long it takes to go 1 mile if you can find a highway with mile markers on it and have a good stop watch. Then do the math to determine your actual speed vs speedo reading.

 

[2X_01_Jeeps]

I get 22 mpg running 68 on the interstate. Profile is 4 miles of 40 mph to the interstate, 30 miles of interstate, 10 miles of 55 with about 3 stoplights I usually catch green and another 4 miles of hill plus 30 mph neighborhood.

Running errands in town drops mileage quickly so that 15 mpg isn't unusual.
Same car, driven by my wife to the grocery store and sewing store (and almost noplace else) gets 9-10 mpg because it's always warming up and never cruising at operating temperature.

In order to compare results, you have to know if you are testing the same way.

(Stock running Michelin tires)

 

[Jeep450r]

96 XJ, AX-15, 4.88's, 33x12.50's, 4.5" lift, bumpers.

From gas station to gas station, exactly 100 miles, at an average of 65 mph revving 2500rpm, I averaged 18.83 mpg.

 

[xjrev10]

Right around 14 mixed driving with stock suspension, AW4, 2000 model with 245/75/16s.

Was getting 18 with 225s.

I get 23 with my 88 MJ 2wd 4.0 (5sp)
Got 18 with my 91 MJ 2wd 4.0 auto

 

[KJurasek]

MPG? Lousy. Between 12 to 15. Enough of a reason for me to consider a LQ4 swap.

I heard some of the mileage problems are related to the AW4. If you swap in a 700 R4, then mileage improves to 19 - 22. Just a more efficient transmission.

 

[jworth]

There's all this talk about a tune up. What's to tune up on an electronically controlled engine? I suppose you can gap the plugs and make sure nothing else is wrong, but what else is there to adjust?

 

[cnjcherokee]

2000 XJ 4.0 AW4 265/75/16s and 3" I've been getting between 12-14

 

[yenkoz]

Yeah dj wether I'm driving all highway miles or commuting back and forth to work my jeep seems to get a consistent 20mpg. Only thing that really seems to kill the milage is starting it up and letting it idle for a few minutes when it gets real cold out.

 

[gdavis]

Recently completed a 2,800 mi. trip with our 97 GC 4.0 auto, totally stock. Trip computer showed 20.4mpg, with run time of 50.1 hrs. It has 77k on it.

The 89 XJ 4.0 auto averages 15mpg, it's mostly used on short trips.

 

[forged]

The 95 XJ Country gets 16 MPG on every tank, and that is with the 21 Mile drive to work each day. I have the 3.55 gears and the 225/75r15 Radials, and 5 rebuilt fuel injectors. No lift or fancy stuff yet, but I might slip in a new oil pump this weekend. It runs real smooth, and has 211,000 miles on the engine, so I have no complaints. Might install my cherry-bomb glass pack this weekend too, and then I can prolly still get 16 MPG but sound like a wound up P-51 Mustang !

 

[KJurasek]

"There's all this talk about a tune up. What's to tune up on an electronically controlled engine? I suppose you can gap the plugs and make sure nothing else is wrong, but what else is there to adjust? "


This is correct. However clean injectors and sensors make a difference. That along with the not so forgotten---clean air filter.

With an electronically controlled engine, everything has to be working just right otherwise the computer will compensate somehow (usually more fuel).

 

[larsen]

15.4 freeway lifted on 31s with a 350 chevrolet & 700r4. Install a vacuum guage and practice driving for peak manifold vacuum.

 

[Ecomike]

I've been driving my new-to-me 97 4.0 auto for about a month. Can't seem to get better than 225 miles per 14.5 gallon fill ups. About 70% city/30% hwy. I take it easy on the skinny. My jeep runs good.

I thought these things got better mpg. Is it just the manuals?

My brother's 99, gets 340 per 18 gallon fill ups consistently.. and he's got a 3.5 RE and 31s!

WTF??!!

What is everyone else getting on their 4.0 auto?

Read up on testing the O2 sensors here (old post I made in this forum). They can get tired and slow and eat into the mileage big time, with out throwing any codes. Old plugs, wires, cap, rotor, air filter, can eat mileage too, with out throwing codes!

 

[Miller88]

Between 16 and 20 highway.


Last tank: 10mpg. but it's been all short trips of about 2 miles or so.

 

[loki36]

Mine got 17 on the last tank. Almost 16 tank before that. Was getting 11 until fuel system treatment a few weeks ago

 

[tom11919]

Last 1000 mile road trip was a low of 17ish going over the Smokies in Tennessee and a high of 19ish across Ohio. (quick calcs at the pump and compensating for the tire size throwing the odo/speedo off ~10%) Mine is a '97 with ~120k on the clock, 4.0l, AW4, 231, factory 3.55 r&p's in the D30 and D35, about 3.5" of lift, and 31" BFG ATs. I'm curious to see what it'll be with the 8.8 and 4.10s I've got on deck.

 

[remat]

Interesting thread. I get 18-20 mpg with my stock 2000. That's a pretty even mix of freeway vs city. Tires are P215's AS.