How many miles on a tank?

What kind of mileage does everyone get out of a tank? I'm running 31 tires, 5" lift and 3.55's and getting about 250 miles, depending on the driving. I need to regear soon and think that the mileage should improve, we'll see.

Depends on the driving that I'm doing. I would guess I can do a little over 300 at best.
I did notice something interesting once, and that is when I'm closer to sea-level that I don't get as good of gas mileage as when I'm at home (mile-high). I don't know how altitude can affect gas mileage, but it does...

If I keep my foot in check, I can get 260-280, if not, more like 210-230. This is a '99 with 3.55, 30's, and 3.75 lift.

400

Rev



*Aero tank....32gal

300+ - could be more but I'd have to drive like an older gentleman.

'88 XJ, stock with 225/75 tires and 3.07 gears gets 23 MPG highway.

'88 MJ with 31x10.50 tires and 3.73 gears gets 19 to 20 MPG highway with the tailgate up.

I think i need to do something then because i get like 15-18MPG and i do mostly highway driving and i am running 30X9.5 BFG AT with no lift and stock gears or is that normal??

To all who are worried:

May I suggest that you do some real MEASURED and CALCULATED fuel economy tests before you jump to the conclusion you have a problem.

For example, what you "think" is 15-18mpg may actually be closer to 18-20, and that would not be totally out of an expected performance range for a typical "stock" XJ.

Also, on a typical XJ, with a 20 gallon tank, it probably reads "E" when there is still 2-3 gallons left in the tank. Gas guages tend to be conservative--there is nothing more agravating than to run out of gas when the guage says 1/8th of a tank is left!

Thus, the typical owner is only actually using about 18 gallons of fuel when he reaches "E". At 18 mpg average fuel economy (combined city/highway), that equates to a range of 324 miles.

I would also bet most of us don't actually wait until the needle on the guage is on "E" before we fill up. So that means we are really refilling when there is maybe 3 or 4 gallons left, not 2, thus making the total refill closer to 16 gallons.

Sixteen gallons at 18 mpg is a range of 288 miles. That sounds like the kind of range many drivers of XJ's report, and yet think they have problems.

old88xj said:

I think i need to do something then because i get like 15-18MPG and i do mostly highway driving and i am running 30X9.5 BFG AT with no lift and stock gears or is that normal??

Click to expand...

Did you change your speedometer gear to adjust for the larger tire size? If not ... the difference between stock tires and 30x9.50s is 6%, so if you still have the original speedo gear, right off the bat your actual mileage is more like 16-19 MPG. Then there's the issue of how hard/fast you drive. I cruise at the speed limit -- gas mileage drops off very quickly when you push a rolling brick over 70 MPH.

I average 320 per tank. Slightly more if its all highway driving and less in town.
97, 4.0, 5 speed, 3" lift ,30x9.50 BFG, k&n cone filter, 3.07 gears

288 for a full tank, 33 Swamper Radials, 4.10's, AW4, 6.5" lift. The gears really helped this out. I haven't changed the speedo gear yet, can't seem to find one for a 242 t-case. But still looking.

I read a thread somewhere the other day about the fact that the 4.0L is a happier motor revving closer to 2500 rpm than at 2000 rpm. I can see the the logic and I'm trying it out now, fresh tank of fuel, trying to remember to run in drive instead of o-d with the AW-4.
Think the jump to 4.10 would help? Going to regear anyway, just curious.

I used to get 22 to 23 MPG when I was stock but it went way down when I went to 32s (3.07 gears & 32s= 4th gear on highway), like 14 to 15. When I switched to 3.55 axles from an auto donor, that put me right back to the equivalent of stock tires and 3.07s. I now get 19 to 20, occasionally 21MPG. I was getting 13 when my map sensor went bad though! So, I fill up right about 300-310 miles and the light is just coming on. It usually takes about 15.5 gallons. I have run it with the light on for 56 miles once!! That gas stop took in almost 19 gallons.

As for optimal RPM range mentioned above, I cruise at right about 2100 in 5th and it is perfect. I am pretty sure that if I ran it in 4th at 2500 my gas mileage would go down.

All highway, from a full tank to empty (stalled out in the driveway) I mustered 378 miles out of that 20 gallons. Thats with 31" TrXus MTs, 3.55s, corrected speedo, and the cruise set to about 72.

--Matt

Stop Stop Stop :

You're killing me. I only have the 13 something gallon tank.

Even before I lifted my rig and went to bigger tires and was getting up to 25-26 MPG, I never could go more than 300 miles with barely 1 gallon reserve. Now that I'm getting 20 MPG or less on the highway (and much less, when wheeling) I have actually filled up with just over 100 miles (there was still more than 3 gallons in the tank - but I didn't get much better than 10 MPG . . . this was going 2 to 3 miles per hour at times in low range, and with the air conditioner on).

Even with a "jerry can", I have 2 - 3 gallons less than you folks do.

245/60R15's, no cat, full exhaust, no emissions, other mods, lightened mildly, i get about 180-190 to a tank.