Horrible Gas Mileage - Solutions?
 

My gas mileage in my 1998 XJ (at 257,000 miles, with a 2-inch lift and 225's) was approximately 22 mpg on the highway. A beautiful thing.

My recently purchased 1999 has some issues with trashed or nonexistent front suspension bushings, 31-inch tires, and 4-inch spacers in the front. My highway mileage on the return trip from SLC was...15 mpg. Yikes!

I'm wondering what y'all have done to remedy gas mileage like this. I suspect that replacing my bushings, a grease job, a tune-up, removing the 4-inch spacers, and smaller tires will improve my mileage. I just hope I can get it back over 20 mpg!

I adjusted the tow of the front wheels 2 days ago.

[On a side note, is it strange to have 4-inch spacers in the front and apparently nothing but stock springs in the rear? She sits level.]

How sure are you your 99 got 22 mpg ? Have you ever checked the miles driven against the fuel used, and I mean with something other than the odometer.

I ask, cuz I thought my 96 did too....till I found out the factory speedo was off......by almost 10% when checked with GPS.

Now, with 31's, and no speedo correction of any kind, it is only off ~ 2 mph @ 60.


If it sits level with 4" spacers up front, it has 4" lift springs in the rear as well, or a longer shackle, or some combo thereof.

And are you sure they are 4" spacers, and not a 2" spacer and the factory bushing, which kinda looks like a spacer ?


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Getting 15mpg on 31" tires is not terrible. 18mpg would be a pretty good ball park figure for a stock XJ (perhaps as much as 20 if it was all level highway). The number one thing you could do to improve is to come back down from the 31" tires. It's not just the diameter that robs power (depending on gearing), but they lay down 1" (or even more) per tire in tread width. That is 4+ extra inches of tire (width-wise) that the vehicle has to push around. Switch to a 30x9.5 (or equivalent metric size) and you will likely appreciate the increase in efficiency, as well as acceleration.

Is that hand calculated? 22 mpg is high, 15 mpg is about normal.

My '00. CA Emissions. Stock except for a 4 hole injector upgrade. 225 75 15 Cooper Discovery HT's. With some weight added to her in factory options she did not come with. All 3 skid plates, factory running boards with rear mud flaps, full size spare, removable head rest buckets with power seats on both sides. She does have the roof rack. In the last 5 years she has had new shocks, replaced all 4 O2 sensors, plugs, the tires I mentioned before, dual cat back exhuast replacement, trac bar, steering damper, and had an alignment.

I mention all this so you will have an idea of where my XJ is at. So using the cruise, which I also added, and taking it easy on the skinny pedal I get about 22 MPG on longer highway trips. Calculated by hand and pretty much corresponds to what my overhead console rear out is. Never calculated around town but the overhead reads just under 15 MPG.

I think as far as around town goes that is normal for a stock XJ. The highway mileage is better then I had thought it would be. Let us face it. Might as well be driving a billboard down the road.

Ahh! The 4-inch leaf springs make sense. Maybe I'm dense but since that isn't obviously apparent to me I never would have thought of that...well probably after reading more posts on CF. I will look more closely for factory bushings.
And yep I checked the mileage of my '98 by recording gallons and miles driven. My speedometer was not off either, according to the check on I-80 in Utah (those are always fun). It was between 21 and 22gpm.

Smaller tires is my plan. I don't like the ride or noise level of the 31's.

As far as gas mileage, the theme seems to be "Remedy? Remedy what? 15mpg is normal." Ha, well, thanks guys. Aim for the best, I always say. :D

Thank the Lord...

:D Love XJ's, just trying to make the best out of a gas guzzling situation. Sounds like you've done very well! The background is helpful. I also own a 1983 Chevy Silverado which gets approximately 11mpg. One super porker is enough, I figure. :D

Silly question, what gear ratio are you running with the 31"s?

Im still chasing my poor fuel mileage. 235 sized tires on Upcountry level suspension and im averaging 13.2 mpg. :(

I don't know how to figure that out ha. Do tell...

Woah!

Yeah I've had 4 XJs and this is the ony one that's been that low. All the others have been high teens with one avg 20 even.