Mr.Cherokee

Silly question from a novice jeep owner. I somewhat recently (5-6 months ago) upgraded my jeep to a 4.5in lift and 32' kenda klever M/T's. Now, I am sure everyone knows about the 20 gallon gas tank. About 3 or 4 months ago i was getting a steady 205 miles to the tank (still suckie), but more recently it seems like the jeep is at a steady decline. I have about a gallon left at 170 miles, and it even died at 160 miles a couple of days ago. I FILL it up all the way every time. Oh, and to top things off, the gas gauge stopped working for some reason. I am aware there are a plethra of reasons as to why jeep os trying to make me broke, but I would love to know if anyone else ever has this problem/or anyone who can help me come up with some idea so i can stop bleeding money.
Thank you lots and lots!!

MonacaYankee

You are going further than the miles are registering. There's a chart to get the actual mileage depending on tire size but I am not finding it. Sounds like you have bigger issues than that though.

Mr.Cherokee

What are these bigger problems you speak of?

Radi

Tire size alone is introducing about a 14% error.
What year, engine and trans do you have? What is the calculated economy you are getting? Miles driven/fuel used.
How about tune-up items? How old? Any codes stored, presuming yours is capable? (don't know the year)

investinwaffles

I was told 33's throw things off by about 15% so around there.

Start with replacing the o2 sensors if you think its worth it. I forget which one is the important, but apparently only one needs to be changed (or two if you have a cali-compliant vehicle). Upgraded will help a little bit as well, as will having a strong ignition system.

letsgomuddin

Truthfully,its going to be hard to get exact mileage with your speedo being off due to the tires. Theres a chart online that tells you what speedo gear you need to use for what gear and tire size. Its an easy swap btw. As far as you mileage, its winter time which means winter blended fuel and more of it to keep your jeep running. A decrease in economy as the temp drops is normal.

cherokeeyed

To the response about the 02 sensor, the upstream 02 is the one that is important as it controls your Air/Fuel ratio. Unless it is bad, it won't have anything to do with your issue. Plug a scanner in if possible (depending on year) and read them, make sure they're switching correctly.


Does your Jeep have a thermostat? Is it the stock thermostat? With the colder temps floating around the U.S. it means it will stay cooler for longer. When these jeeps run cold they tend to burn more gas.


I've run 35's on stock geared autos for a long time, they suck lots of gas, not sure on the exact mileage I get with the 35's but I don't miss a gas station very often. These 4.0's regardless of tire size will suck lots of gas in general if you are giving it a lot of gas.


I always thought on 32's mine did great on gas.

highmileage

If you were getting 205mi to the tank with 20 when it was full you have more issues than tire size and a lift. In bone stock form and 4x4 you should get at least 17mpg, and in a stick at least 20mpg(hwy) 15ish in town. I average 380ish a tank.

tokelyn

Please tell me how I have a 88 xj on 33 and I get barley 200 mile to a tank
( I have a lead foot but when I'm not galling *** I still don't ever get more then 200 miles to a tank)
Yes I've ran a hole tank of gas w/o being a lead foot an it still sucks my wallet empty

skife

my odometer says around 250 miles per tank, usually around 14.8 miles per gallon, average fill up is something like 14-17 gallons.

I use aCar to keep track of some of my expenses

salad

Hey mister OP!

We've established that you have a Jeep XJ but not any other details. What is the engine, year, and transmission? These things were made from 1983 through 2001 with 7 engines, 8 transmissions, and 5 or 6 fuel management systems... that's a lot of guessing.

highmileage

I cannot speak for all 4.0s but with mine;
spend some money on the ignition spark means everything, any up-scale coil will help.
use quality plugs that match your ign coil output,
wires that do the same, good cap and rotor, in your ignition system parasitic loss kills.
Do the inj. swap you'll be better for it. Saw a 1.5mi bump when I did this.
Is your emissions system working? if not fix it. All of our jeeps have it and it won't really run right w/o it, may seem like it but not. Do not neglect the EVAP canister that is an open outlet for your gas tank and fuel system.
Fuel filter, may not seem like it but a dirty one will affect mileage.
And anything else you can think of that will give your #s' a bump.
With my time and energy in having dealt with and owning lifted vehicles in the past, I only saw a 3 to 5mi loss in fuel mileage(sticking with stock gears) and most of that loss was in town driving.

BlueRidgeMark

The first step to solving a gas mileage problem is to stop paying attention to "miles per tank".

Your gauge is not accurate enough to make that even remotely meaningful. Add to that the variability of the pump shutoff mechanisms, and you have a recipe for being lied to.

The only way to properly track your mileage is to record your odometer readings and the gallons pumped each time you add gas.

If you are doing "miles per tank" you really have no idea what's going on. Worse, you think you do.



aCar is a great app! If you have an Android phone, get it!

hedbutter

Also check your four wheel alignment. My parents bought a car and they were getting terrible mileage. Took it too the shop and something was out of alignment, they saw a 2-4 mpg increase.

black_771

Okay. I have had my XJ for about 4 years, but it sits undriven until winter. I have never really needed to drive around fulltime in 4WD for several days until this week. I usually get about 13mpg in 2WD. I just recently changed the fuel filter and cleaned the throttle body with spray cleaner. This happened just before the winter storms so I have no recent 2wd mileage numbers to compare to, but in 4WD now, I am getting only 8 mpg, again down from 13 in 2WD.

Is an almost 50% drop in mpg in 4WD normal? Would throttle body cleaner cause a drop in mpg?

I literally have to fill up the tank now every 2 days and it sucks.