Bad gas mileage?

[raphaelchicago]

I recently drove my 2005 jeep TJ rocky mountain edition 6 spd with 4.0l. It has a 4 inch suspension lift and 2 inch body lift. Running 35inch tires. I just drove from thunder bay ontario to airdrie alberta and got a maximum of 290km on a full tank. The trip is about 2100km. Also every time I would fill up the jeep would take longer to start but only after I get gas. I was thinking bad filter? Or is this just something i should expect.

 

[Chris]

What gear ratio do you have?

With 35s, a 6" lift, and improper gearing, your fuel economy isn't great, but it's about what I would expect.

The starting issue is unrelated. Are you throwing any check engine lights?

Guarantee you this has nothing to do with your filter.

When is the last time you changed your spark plugs and O2 sensors? Your O2 sensors for instance should be replaced every 80k miles or so, regardless of whether they are bad or not. They directly impact your fuel economy. That being said, if you don't know when the last time they were replaced was, do yourself a favor and replace them.

You'll find this thread helpful:
The Official Jeep Wrangler TJ Oxygen (O2) Sensor Thread

 

[Jerry Bransford]

The number of miles/km seemingly available on a tank is often caused by an inaccurate gas gauge which is common on a Wrangler. The only way to really know what range is actually available is to calculate the mpg you're getting by dividing the distance driven by the gallons/litres required to fill it back up. A TJ's gas gauge pointer commonly erroneously indicates it is near empty when it's really more like 1/3 to 1/2 full.

 

[raphaelchicago]

I'll have to look into the 02 sensors just kinda sucks that I'm on a trip right now and all my tools are at home. My gears are stock this is what I looked up for my model.

 

[raphaelchicago]

I have no check engine lights and get no codes when running a scanner.

 

[raphaelchicago]

I believe the has guage is on when I was in Brandon the tank took 70l and I was almost completely out when I pulled in. I believe I have a 72l tank.

 

[glwood]

I'll have to look into the 02 sensors just kinda sucks that I'm on a trip right now and all my tools are at home. My gears are stock this is what I looked up for my model.

View attachment 76146

I think @Chris meant axle gear ratio.

 

[Chris]

I think @Chris meant axle gear ratio.

Correct, I meant axle gear ratio.

The wrong gear ratio with 35s could definitely cause a big hit on your fuel economy.

 

[pagrey]

Your tank is 73.8l
You had about 3.8l remaining in the tank when you filled it.
You were getting 9.8 mpg (24 l/100km) if your mileage numbers were correct which is a bit low.
If you haven't calibrated your speedometer/odometer for the larger tires you are really getting 11.4mpg (20 l/100km) which isn't bad for 35" tires.

 

[Mike Jackson]

Also need correct speedometer gear to calculate gas mileage.

 

[steelhd]

You'll find this thread helpful:
The Official Jeep Wrangler TJ Oxygen (O2) Sensor Thread

That is some good stuff, thank you! I have a lead foot so haven't been shocked by my highway mileage. Pushing a lifted armored square sail down the road at close to 80 mph will never be good for the wallet. But my terrible trail mileage has been surprising in a not so good way.

 

[RaymondT]

km/ltrsX2.83=mpg (imperial).

I have gotten 28mpg on the 4 banger straight hwy on summer gas taking it easy 90kmh/55mph. That would be about 23.3mpg US gallons for our friends south of the 49th. I doubt you could get much better in a TJ brick.

 

[Rob5589]

For your combo, do not expect much more than maybe 12 mpg, or whatever that translates to.

 

[D M]

What gear ratio do you have?

With 35s, a 6" lift, and improper gearing, your fuel economy isn't great, but it's about what I would expect.

The starting issue is unrelated. Are you throwing any check engine lights?

Guarantee you this has nothing to do with your filter.

When is the last time you changed your spark plugs and O2 sensors? Your O2 sensors for instance should be replaced every 80k miles or so, regardless of whether they are bad or not. They directly impact your fuel economy. That being said, if you don't know when the last time they were replaced was, do yourself a favor and replace them.

You'll find this thread helpful:
The Official Jeep Wrangler TJ Oxygen (O2) Sensor Thread

I just learned that the gearing can help with mileage because I have 33s with 3:73 gears and its not the best. Its supposed to be 4:56's for 33"s right? I also have a 5spd manual so wouldn't that cause my RPMs to be higher, and by how much?

 

[Chris]

I just learned that the gearing can help with mileage because I have 33s with 3:73 gears and its not the best. Its supposed to be 4:56's for 33"s right? I also have a 5spd manual so wouldn't that cause my RPMs to be higher, and by how much?

See the chart I made here for gear ratio:

What gear ratio should I install in my Jeep Wrangler TJ / LJ? (and other re-gearing FAQs)

Your RPMs for cruising on the highway should be around 2200-2500 RPM ideally. Of course after re-gearing your speedometer will be off, so you'll want to take care of that using this how-to guide:

How to recalibrate your speedometer after changing tire sizes or gears

 

[D M]

See the chart I made here for gear ratio:

What gear ratio should I install in my Jeep Wrangler TJ / LJ? (and other re-gearing FAQs)

Your RPMs for cruising on the highway should be around 2200-2500 RPM ideally. Of course after re-gearing your speedometer will be off, so you'll want to take care of that using this how-to guide:

How to recalibrate your speedometer after changing tire sizes or gears

Awesome, thanks