I couldnt get that with stock... driving like a grandpa The best on stock I could get was 20.

 

I'm getting 15city /19 hiway with my XJ 3.55's and 31's

 

31s I get about 14 not sure on the highway. I find I can justify keeping it my dd as long as I never accurately check the mpg.

 

31x10.5 firestone destinations about 8-12 mpg 8-9 in town 10-12 highway, i have a stupid 3 speed trans, i need a 700r4 soooo badddddd

 

how are you guys pulling that off?? my xj is stock on 225s and i'm getting avg 15.5 mpg. once i go to 31s, it's going to get worse.

my friend has a '97 auto 3:55s on 31s and he gets 11 mpg. he's sad.

 

31"x10.5" BFG All-Terrains on a stock '95 XJ sport. 4.0L, auto trans, C8.25 rear end with factory 3.55s. Trip is giving me ~14mpg, BUT the speedo read about 13% off (I think that's what the calculation is) so Its probably around 16-17mpg with normal driving. Steady cruising at 45mph (when OD kicks in) the motor only turns 1600-1800 rpm and my mileage goes through the roof. And on the highway spinning 2000rpm the mileage is better but not as good as 45mph...I wish I had a 5 speed so I could control where it shifted for best fuel economy, rather than the computer controlling it for best power when you don't need it. Oh and my mileage readings were on a cap and rotor, and wires with 200k on them. And the plugs had about 85k on them. So it wasn't running the best. Though I did notice that running a good brand name injector cleaner boosts mileage a few mpg, worth the extra $2 a fill up.

 

I have stock tires on my '97, but with the 5 speed I pull of VERY good mileage.

Maybe you need to do some maintenance or possibly some dirty/clogged injectors?

 

Hope you guys with the bad gas mileage didn't remove the cat and put tape over the check engine light so you didn't have to look at the o2 sensor codes... xj's don't seem to like that, lol.

 

seafoamed the jeep, air filter is new, plugs look good. i think the autos just dont compare for mpg.

 

I love my 31's BFG's. I keep them properly inflated and run a 4.7 stroker. I average 17-18 mpg. Hopefully the change to 31's will help your mileage. Good luck.

 

I drive like an old man if that makes a difference. Also use 89 octane. I really can't complain at all on the mileage, it almost compares to the S2000.

 

After I changed the cps and plugs, wires, cap and rotor I went for a nice long ride...all highway between 55 and 65mph with BFG 31 a/t's, I only burned just under half a tank in 185 miles (with the 31's)...so that's around 18-19mpg. Not too bad, and I have yet to clean out the throttle body and crap in the intake, or change the fuel filter...22mpg is my goal.