too much gear= bad mpg?

[in4aride]

fully loaded for a week of camping and wheeling
96 4.0 aw4 STOCK GEARS and 35's i cruised 70-80mph and got roughly 25mpg....

on the freeway the bigger the tire the more ground you cover with less rotation of the tire....a 33x9.50 would save you the weight and still step you up ain diameter to cover more ground, but 1" diameter and the benefits/downfalls of the circumfrence change hardly seems worth the price of extra tires and wheels :dunno:

 

[WaXJ_Skier]

31's and 4.56 should be fine, the AW4 has a a really high OD, best thing you can do is keep the speed under 65. 55-60 was my sweet spot with 33s and 4.88s and an AX15. With 31s and 456 you are turning about 2700 @55 thats not bad I run my DD in 3rd on the freeway for 31s and 3.55 and get about the same RPMs.

 

[WaXJ_Skier]

fully loaded for a week of camping and wheeling
96 4.0 aw4 STOCK GEARS and 35's i cruised 70-80mph and got roughly 25mpg....

on the freeway the bigger the tire the more ground you cover with less rotation of the tire....a 33x9.50 would save you the weight and still step you up ain diameter to cover more ground, but 1" diameter and the benefits/downfalls of the circumfrence change hardly seems worth the price of extra tires and wheels :dunno:

I call bullshit, unless you were going down hill in a vacuum.

 

[in4aride]

nope, its 25 miles up hill (got about 16mpg there, damn mountain passes)
then a long flat drive for 90 miles or so, and tho whole trip took right at 1/4 tank. i can get about 17-18 gallons in a tank, divide by 4 gives ya about 4.5.

take an approximate 115, divide it by 4.5, and you get 25.5.

thats locked front and rear, 35x12.5 with about 34psi, tent, coolers, spare parts, spare tire, tools, clothes, and two people...

 

[XJLI]

nope, its 25 miles up hill (got about 16mpg there, damn mountain passes)
then a long flat drive for 90 miles or so, and tho whole trip took right at 1/4 tank. i can get about 17-18 gallons in a tank, divide by 4 gives ya about 4.5.

take an approximate 115, divide it by 4.5, and you get 25.5.

thats locked front and rear, 35x12.5 with about 34psi, tent, coolers, spare parts, spare tire, tools, clothes, and two people...

i can give that to ya... i dont remember where we were but somewhere in colorado sam and i both got magically high mpgs... like mid 20s for each of us. must be the awesomeness that is embedded into the state's geology.

 

[srmitchell]

I can believe that.

There were a few times where I drove down to hollister on 31's, 3.55, fully loaded, and I magically got 23 mpg.

It was 90 miles and I barely hit 1/4 tank of gas used.

 

[XJEEPER]

fully loaded for a week of camping and wheeling
96 4.0 aw4 STOCK GEARS and 35's i cruised 70-80mph and got roughly 25mpg....

Was your trip downhill, both ways, with a tail wind? NO SALE.

 

[XJEEPER]

yeah its aw4/4.0, and currently on 32's it seems to get real bad gas mileage, currently i topped off on gas and am waiting to go fill back up to see how many mpg i get, but im gona need help doing the math because my speedo is way off, it says that im going way faster than i really am i think

How can you expect to make an educated decision on gearing if you cannot accurately measure your fuel economy with an accurate speedo?
Do you own a GPS?

 

[ktm racer 419]

i can give that to ya... i dont remember where we were but somewhere in colorado sam and i both got magically high mpgs... like mid 20s for each of us. must be the awesomeness that is embedded into the state's geology.

that was from ouray to co springs iirc

it seemed to be mostly downhill, but there were some pretty intense uphills.

and i remember driving uber fast. i hit the governor on multiple occasions

and colorado sucks for having a quick jeep. 0-60 in like twice the time it takes here at sea level.

i think we were high up enough in the mountains we hit a jet stream or something lol

 

[foxwar71]

i dont remember where we were but somewhere in colorado sam and i both got magically high mpgs... like mid 20s for each of us. must be the awesomeness that is embedded into the state's geology.

FACT!!!


with my 35's and 4.56's in a loaded xj, i could knock down low 20's going from wyoming down the denver airport. if i found a truck to follow and draft, mid 20's appeared. on the other hand, driving north in CO usually sucks down gas more and you get more wind resistance it seems.

 

[WaXJ_Skier]

that was from ouray to co springs iirc

it seemed to be mostly downhill, but there were some pretty intense uphills.

and i remember driving uber fast. i hit the governor on multiple occasions

and colorado sucks for having a quick jeep. 0-60 in like twice the time it takes here at sea level.

i think we were high up enough in the mountains we hit a jet stream or something lol

could be the reason you get decent mileage, less air density = less fuel required for combustion.

 

[kastein]

if it says ur faster then u really are then ur already overgeared from stock. what i find amazing is people who get as much as or more than the amount of mpg that stock xj's do. if ur getting 20 mpg on 35s thats ungodly since 20 is about the most a stock xj will get. im always blown away by the fact that people seem to atleast think they get stock mpg on big air sails such as an xj on big tires and a lift

I pulled 23.31mpg in my stock MJ, 225s, 3.55s, AW4 with 220+k miles on it and no rebuild, 4.0 with 220+k miles on it and no rebuild, with 1500lbs of cargo. That number was calculated using the amount of gas I added from a full tank to a full tank, and the number of miles I traveled according to GPS and my odometer (my speedo is within 0.1mph of GPS reading with the 225 tires.)

Not aimed at any specific person, but if you are arguing mileage and going by "half tank" "quarter tank" you need to stop being an idiot and use the full tank to full tank measurement method, the gauge is NOWHERE NEAR accurate and you are only confusing things and misleading people.

Method:
Fill tank. Don't top it off, don't do anything, just fill it till the pump stops.
Reset trip odometer.
Drive.
Fill tank again. Don't top it off, don't do anything, just fill it till the pump stops. Divide miles driven by amount added to tank.

You will get the most accurate results after several tanks by averaging your numbers and filling up using the same pump at the same station as much as possible. Obviously on road trips you have to accept some pump to pump inaccuracy.

 

[1990JEEPXJ]

nope, its 25 miles up hill (got about 16mpg there, damn mountain passes)
then a long flat drive for 90 miles or so, and tho whole trip took right at 1/4 tank. i can get about 17-18 gallons in a tank, divide by 4 gives ya about 4.5.

take an approximate 115, divide it by 4.5, and you get 25.5.

thats locked front and rear, 35x12.5 with about 34psi, tent, coolers, spare parts, spare tire, tools, clothes, and two people...

seems like a lot of rounding and guessing and trusting the factory gauge. i assume your speedo is off because of the larger tires as well. why can you only get 17-18 gallons in?

 

[srmitchell]

Kastein is right. My gas gauge is awful.

I fill it up, and I start it, and the gauge goes down.

Even driving to school (4 miles) it goes down, then later in the day, it goes back. POS

 

[Starboard M]

I must be driving on the wrong roads in CO. I average about 15-18 mpgs on mainly freeway driving in a 99 with 2'' of lift and 30'' tires.

Between Denver and Fort Collins I get 17mpgs consistantly. Going skiing I get 15 mpgs or less, depending on how many people are in the Jeep and if I want to go faster than 55 up the hills.


Either you guys have magical Jeeps or your numbers are off.

 

[playwithit]

4.88's and 35's, my speedo is dead on according to my GPS and I'm running the stock speedo gear. I'm getting around 20mpg on the highway.

Nice trick with the thirty-fives. Stock and new the 96 xj will get 20mph on the freeway. With the weight of the tires and the wind resistance of the lift, you should have lost a good deal of mileage.

 

[in4aride]

seems like a lot of rounding and guessing and trusting the factory gauge. i assume your speedo is off because of the larger tires as well. why can you only get 17-18 gallons in?

ive hit the tank a time or two, even with a gas tank skid i bent it in on itself a bit (i dunno, i dont know how the F that happens either)

ok well if its any relief to you, i get 15.2-15.8 gallons of gas in the dd when i fill it up, i am all stock auto with 228k, and i just rocked 334 miles out of a tank. on course to do it again, and being on 30's the milage is actually more than that...
334 divided by 15.5 (thats right in the middle) is 21.5 mpg.....thats everyday driving, most of it NOT on the freeway

 

[in4aride]

Nice trick with the thirty-fives. Stock and new the 96 xj will get 20mph on the freeway. With the weight of the tires and the wind resistance of the lift, you should have lost a good deal of mileage.

weight of the tires is a factor in GETTING them moving not KEEPING them moving, an object in motion stays in motion, they will keep themselves going. and with stock gears the tire is covering a greater distance by i believe it works out to 25% on 35's, so if the trip meter reads 250 its actually 300, make sense? gotta look at it all, not just one side of it...

here, from springs to wheeling spot, 50 miles, i could drive there, wheel, and drive back on just over 4 gallons. did it repeatedly
http://www.mapquest.com/maps?1c=Col...=CO&2y=US&2l=38.424999&2g=-105.022202&2v=CITY

 

[playwithit]

weight of the tires is a factor in GETTING them moving not KEEPING them moving, an object in motion stays in motion, they will keep themselves going. and with stock gears the tire is covering a greater distance by i believe it works out to 25% on 35's, so if the trip meter reads 250 its actually 300, make sense? gotta look at it all, not just one side of it...

here, from springs to wheeling spot, 50 miles, i could drive there, wheel, and drive back on just over 4 gallons. did it repeatedly
http://www.mapquest.com/maps?1c=Col...=CO&2y=US&2l=38.424999&2g=-105.022202&2v=CITY

Higher rolling resistance = less miles per gallon

If your logic is correct, the prius and smart car would be rolling on 40" mudders to improve gas mileage. My jeeps gas mileage has gone down from the day I bought it (stock) and that is the price you pay to have a capable 4x4.

 

[in4aride]

Higher rolling resistance = less miles per gallon

If your logic is correct, the prius and smart car would be rolling on 40" mudders to improve gas mileage. My jeeps gas mileage has gone down from the day I bought it (stock) and that is the price you pay to have a capable 4x4.

take two tires, a 215/55/16 and a 33/10.5/15, get em both rolling at 30pmh and let me know which one goes further. thanks try again....

no they run on small tires so the electric engine can turn them in turn not burning fuel for the the good gas milage, but nice try....

and that sucks, guess my jeep wasnt capable, cuz i was getting great gas milage on the freeway(not so much in town)

and im not trying to be a dick, im just tired and in the mood to be a bit facetious is all :thumbup: