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What mpg is everyone getting w/an auto xj?

djlarroc

NAXJA Forum User
Location
Denver, CO
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?
 
About 18 MPG in our 1991 4.0, automatic, a lot of highway driving and a good bit of city mixed in.

Although after the new injectors it was closer to 20 mpg for awhile. My old 1985 2.8 V6 5 speed does a hell of lot better MPG wise.

You might run a injector cleaner and check the air filter.
Thinking back we we first got this jeep after a oil change we'd actually see better mileage.
 
make sure that you check your oddomerter vs the mile markers on the side of the road, with 3'' bigger tires mine was off 3/10ths of a mile, i was actually getting 3-5mpg better than what the regular mpg formula gave me.
 
I'm real anal about tune ups. Quality/matched cap and rotor. Fresh air filter, good wires, and plugs gaped to spec. . I also run Berrymans through the tank before every tune up. Wifes stock 89 AW4 gets 22-24 mpg depending on winter/ summer blend.
 
I don't even bother checking my XJ. I get between 17-18 in my ZJ and about 16-17 in my WJ. All 3 Jeeps are auto 4.0 L. I know that isn't what you asked, but it's all I got! :wave1:
 
I have an 89 xj with 3.55 gears on 31" mud terrains... I have 245k miles and I get about 12 in town and my last trip to the beach including about a 5 mile climb up a 7% grade twisty turns etc I got 17.7 mpg... Ive owned it since 8-8-11/ 241k miles and I have yet to do a tune up just an injector cleaner and oil change.
 
2000 XJ with 235s I can get 17mpg on average.

High speed (70-75) HWY to work and 40-50 around the city average. I can randomly get almost 21, but it just :boom: happens. Granted I do need an air filter (saving for a cowl intake) and I just put a Flow50 and new convertor on it, so we'll see what happens. Always up on maintence; 5k oil changes/tire rotation; new plugs 10k ago
 
My previous '94 4.0 AW4 got 18 consistantly with a 40 mile round trip to work. I had a throttle spacer on it, and that was it for the mods, and I got 18. I plan on this '94 to change the exhaust header for a performance unit, and a high flow cat and exhaust. I will add a throttle spacer and a FIPK/cold air intake and see what it will get. Both jeeps are running 30x10.5x15 tires with the stock gears. My true goal is to get the most mpg out of it, and still work well on light trail duty. I am shooting for at least 20, more if I can. This one also has cruise control, so that should help some. First I need to get the no spark/no start issues fixed, and then I should be in fine shape to get some of this stuff done/going.

Jeff
 
It frustrated me everytime that I checked it so I stopped keeping up with it.

Last I checked my 93 got about 17 and my wifes 98 got 16. Both of us 50/50 city/highway.
 
I've gotten 20 before, but it's rare. If I'm on highway doing no more than 65, I can get that. 75 mph eats it up though. In town I average about 14. That is on a stock 94. Only thing that is not stock is the 235s rather than 215s. I always hear people getting significantly better mileage than me and I have no idea why. I'm not a lead food either.
 
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Most of those averages are better than mine. Forgot to mention, my jeep is bone stock, on 225/75/15. Seafoamed when I got it, and the air filter is new. Runs pretty good. Not sure what's off. I would expect to be getting about 18 mpg at least.

Another friend who has a manual, said when his was stock, he'd get close to 400 per 18 gallons. Now, on 33s and 3:07s, still manages 300 miles.

I think I want a manual. :)
 
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.
 
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.
 
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.


Anyone know if a clogged cat convert could kill MPG?
 
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.


Anyone know if a clogged cat convert could kill MPG?

yes, stops air flow, its the opposite of performance exhaust, messes with computer too if you have obd2 and O2 sensor after cat
 
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