seen alot of post about people saying there jeep is getting bad mileage. Im going to post what has helped me. Feel free to add on to this thread with your tips on gaining mpg. Remember your driving a brick on wheels...they are not the most aerodynamic things ever. Here is what helped me

#1. Proper tire inflation...my tires are at 40 psi...most should be around 35 psi. Check your jeep...i bet you have atleast 1 tire that is low.

#2. quality fuel is a must....even tho the mom and pop stores may have cheaper gas...mobil, shell and bp have better quality gas than local stores.

3. Fuel injector cleaner....seafoam thru YOUR GAS TANK will help. do a full can every oil change

4. Quality oil, this is a huge debate on here..In reality, the 4.0 is a tractor motor. Its happy with any oil, as long as its clean. Personally i run synthetic blend which i feel is better than convential. That is a whole different debate

5. This is more lengthy....Here is what i did to go from 14-15 mpg to 17-18 mpg (calculated)
First i cleaned the air filter (duh)...next i ran a full tank of 93 octane gas thru it with a full can of seafoam (to break junk up) After a full tank ran thru, i replaced my dirty plugs with new ngk plugs (or champion coppers work great)
I noticed that they were dirty after the seafoam, SO REPLACE THEM, they are cheap!! (and wires/cap/rotor)
after a week or so with new plugs, replace both upstream and downstream o2 sensors. DO BOTH, i thought just the upper was needed, nope do both, trust me! this will fix your mpg issues, it will fix your air/fuel ratios and make your jeep run 10x better!

6. When you do replace BOTH o2 sensors, reset your ecu, this is easy to do and well worth it

7. While your under the hood, adjust your t.v cable....its free and takes literally 10 seconds.....make a HUGE difference....this is the best thing to do (and you will notice this right away)

8. NO brainer here....drive easier....let it shift under 2k rpms..and set your cruise as much as possibe

Guys and girls, by no means am i a expert....but these all helped me. Try doing them to your jeep in that order. make sure you let the seafoam work for a full tank before putting in new parts. You dont want to put new plugs in and then dirty them up with crap. This is a few week process, but its well worth it. Remember winter blend fuel will bring mpg down, so here is my last suggestion

9. Download the free app to your smartphone called "mileage" its a orange(ish) logo, keep track of every fill up and see what your jeep is actually getting. This will help you notice any "drops" in mpg. If you use this app you will see right down to the decimal what you get per tank. i.e. 17.92, 16.68 etc...

It helped me notice fuel quality....mom and pop shops lowered my mpg almost 1 mpg, and this app keeps a history...so you can see the drop when you use the low quality gas.


Again, im not expert, but try doing these things, In this order, and report back. I think alot of you will be surprised.

Feel free to add your tips....I hope this helps

*remember, let the seafoam work for a full tank before changing plugs or o2 sensors*

for ordering any new parts...use rockauto.com. cheapest place for parts and shipping is fast...

 

Link on adjusting the t.v.? I read the DIY on here once but can't find it =/

 

I dont have the link from here but i do have this, hope it helps:

 

703 injectors
IAT relocate
open airbox under filter
electric fan, remove clutch fan

99+ intake did nothing, changed the power band alittle and made it smoother. No MPG change
Header...no real MPG change

 

nice tips, will try this soon.

 

heres a tip...avoid excessive idling. a few minutes extra every day adds up quick over the course of a couple of months. idling = 0mpg. personally i would like to install an hourmeter in my heep, since i kind of like to let it idle for while when it's closing in on -40 with the wind. (like the past couple days here)

 

Some great tips here. went from 18mpg with 30s to suddenly 14.5mpg. yes, i cried.
TV cable made a major drivability difference. First thing I did when I got my XJ.
Just replaced my upper O2s, ordered the lowers. Will reset the ECU after i install. Relearn the new O2s.

 

report back your results if you can...

I had a rough idle when sitting at stop signs/red lights

replaced both o2 sensors and got way better mpg, more power and the rough idle is gone...

 

Great list - really maintaining good fuel economy amounts to proper maintenance. Most of what you've listed is just keeping things clean and properly adjusted!

Don't forget excess weight. In the words of Marty & Moog from Mighty Car Mods, "you'd probably see better gains if you just took a poo before driving"

As well, vacuum leaks and various seals should be checked regularly.

There are a few mods that can be done to help with economy in certain situations after a Jeep has been modded but this is a great post for the OEM Tech section.

hankthetank, I've also considered an hour meter. I think the 4.0 burns almost as much fuel sitting still as it does when moving. That said I've also left it running while popping into Timmy's on a -30 day

Just to elaborate on this - this may be OBD-2 behaviour only. Renix Jeeps don't have downstream O2 sensors, and the OBD-1 series are suspected to only use the downstream to throw a CEL. OBD-2 however has been demonstrated to use all sensors when operating in closed loop.

 

Hello all, I have a '96 classic, poor mpg! 30"'s, doing a tune up this weekend, guess ill do the o2's also, my question is, I have a header and now it sprung a leak in the gasket, would there be a huge difference in going back to stock exhaust manifold?

 

https://www.cherokeeforum.com/f2/free-quick-fix-41821/

 

Get this meter installed in the cabin. Watch it as you drive:

 

Excellent troubleshooting tool. People rarely use it as such.

 

For those less knowledgeable on vac pressure (like myself, amongst other things) can some one explain how that's going to help?

 

What brand of cap and rotor and plug wires do you recommend?