31's = 15mpg?

[lilredxj99]

Damn, looks like Im heavy on the gas. Ive got 31s and Im averaging 12 highway. Maybe my roofrack has something to do with it.

:idea:

uh huh, I had my tire and jack up there, and was getting approximately 12.x mpg. I took it off and now I'm getting better than 15.6.

I have 31's and 4.11.s...

 

[techno1154]

Hallo. With 31" BFG Muds and stock gearing: 17 mpg. :roflmao:

'92 XJ

That is about what I used to get hauling around about 400# of gear in the back on 30's. Less in hilly terrain. Now with the 4.10 I get 20 MPG. I think 31's will net me a few more MPG's. This is all highway using cruise control and never exceeding 70 MPH.

In 2007 while working in Iowa, I netted 15 MPG traveling between Des Moines and the neighbouring cites on a good day.

 

[wim hoppenbrouwers]

Hallo techno1154. Is it advisable to regear for my Jeep, do you think?

92 XJ 31" Muds

 

[Swamprat]

make sure you have the right gears for your tire size, i was getting hella bad gas milage on 33's with little to no go-power, dropped to 31's and i can drive on a tank for 2 weeks before having to fill it again, and i no have go-power

 

[pfcstone777]

Kind of hijacking topic but did not want to start a new thread.

What are your guys mpg with 35s with 4.88s?

 

[techno1154]

Hallo techno1154. Is it advisable to regear for my Jeep, do you think?

92 XJ 31" Muds

To regear or not is a judgement call each one have to make for themselves. I say that because here on this forum there are many that say 32 tires on stock gearing is as good/better than the stock size tire.

For me 30" on 3.55 was liveable on flat ground stop light to stop light was ok. I do plenty of highway runs of upto 600 miles a day carring 400 to 500 pounds of tools and other gear. Running the hills with the cruise set caused the AW4 to hunt repeatedly for the correct gear ie; 3rd to 4th to 3rd to 4th. That get anoying really quick. To prevent this, I often select 3 on the gear lever. The 4.0L then turns about 3200 RPM. At this RPM gas in the tank do not stay there long. To me, I get the best mileage below 3000 RPM.

I regear to 4.10 a year ago after delaying it for 3+ years and ask myself why did I wait so long to do it. Yea, the 4.0 still turn high RPM's, hifger than I would have liked but now the hills mean nothing to the XJ and get-up-and-go have returned in a big way. I see so 31 or 32 tires in my not too distant future. They should pull the RPM down maybe 200 :dunno: and give me a few more MPG. This is what I am getting now with 4.10 and 30 BFG AT;....

RPM’s at 55 MPH with 4.10:1 gears running 30” tires 1980
RPM’s at 60 MPH with 4.10:1 gears running 30” tires 2175
RPM’s at 65 MPH with 4.10:1 gears running 30” tires 2360
RPM’s at 70 MPH with 4.10:1 gears running 30” tires 2550
RPM’s at 75 MPH with 4.10:1 gears running 30” tires 2700
RPM’s at 80 MPH with 4.10:1 gears running 30” tires 2920

The above speeds were indicated on a GPS.

I also picked up a few MPG using the 4.10 over the 3.55 in both city driving and on the highway. On I-95 from Miami to Boston, MA the AW4 would stay in 4OD with the cruise on at 70 MPH if I do not have to slow down for slower traffic.

In answer to your question, it could be a matter of economics;... the cost of a regear, the cost of fuel, the tire size you plan to use where you drive (hills or flat terrain) and your driving style among other things. Regearing my XJ is by far the best thing I did to it.

 

[UNCC_99XJ]

This is all highway using cruise control and never exceeding 70 MPH.

Using huh? What is this "cruise control" you speak of?

 

[xjh3]

Damn, looks like Im heavy on the gas. Ive got 31s and Im averaging 12 highway. Maybe my roofrack has something to do with it.

Sure does. I was about there and shot up to 16 once I took off my roof rack. I've seen 20 on flat ground with no wind.

 

[jeepfreak1020]

32 BFG AT's with a roofrack and im getting 11, also with stock gears

 

[blondejoncherokee]

i gotta brag a little trip: 290 miles to santa cruz and back to sacto averaging 65, maxxing at prob 75mph, with 33's and 4.88s and lockers i got 17.5 mpg last week for the entire trip. running between 2000-3100 rpms depending on when the slight vibes where coming, not too bad though...i was going by the total distance on mapquest and the amount of gas i bought as i went and not my speedo and not my odo which is off....
pretty decent since with my 3.55's and 31's i was getting 13-15mpg, but that was before a new cap and rotor and plugs and swapping a 195 thermostat back in instead of the 180 thermostat, recalibrated tps, new iac, new coil, cleaned grounds, fixing broken vaccuum lines and putting back on the old stupid rustys air tube with a new K&N tube filter

 

[blondejoncherokee]

i also have a massive roofrack that not only weighs alot but also is wider than the jeep and as long as the roof and very bulky confer everyone says i should pull it off but its too damn convienent

 

[techno1154]

Using huh? What is this "cruise control" you speak of?

It is the little gismo that keeps its eye on the speedo so I could admire the sceneary :clap: or maybe take a :speepin: .

Sorry, forget that last part. :hang:

 

[97Jeepers]

I'm running a stock 225 75 15's for now, but with a few mods to boot. Pacesetter ceramic coated header, 2.5" exhaust, 99 intake, Afe cold air intake, etc.


Its a 97 4 door with Ax-15 and 3.07 gears, i regularly get around 18.9 in town and about 24.5 on the highway, depending if there were hills. My best tank to date was coming back to NJ on the PA turnpike with all of those hills to coast down, I averaged 27.8 MPG!

 

[GordoSmasho]

Did anyone else step in that? It smells alot like bull crap to me....27.8:roflmao:

 

[Muddy Beast]

31's at 12-14mpg. Also about 400 pounds of added steal and material to Jeep doesn't help.

~Scott

 

[fordtech]

Typical 98 Sport- Auto, 3.55s + 31" STTs, skids, recovery points, some equipment in the rear, yakima load warrior rack, no front air dam, heavy right foot..... Dynomax cat-back, regular tune-ups, and Seafoam treatments, newer O2, massaged t-body. I get 12-13 city, not much better highway. Runs like a bat-out-of-hell. Black soot on the tailpipe, not overly uncommon.... Suspect a cracked header, but no symptoms of it.

 

[projectTK]

31's, 3:55's, 89 corvette motor, 15city 18hwy

 

[89xj]

31's, 3:55's, 89 corvette motor, 15city 18hwy

that doesnt seem that good for an engine with about 300hp getting the same as what a 4.0 would get. i guess the positive is the fun you can have with the engine over the 4.0

 

[projectTK]

if it was geared right it would prolly get low 20 with .73 overdrive ratio in my nv4500 trans