Hi everyone,

I'm new to the forum. I've got a 98 Jeep 5.9 , and was curious if anyone had discussed any possible suggestions to better the gas mileage. I average around 12-15 mpg. I would like to keep the Jeep, but I would really like to improve the mileage to atleast 20 mpg if possible. Anyone tinker with changing gearing, performance manifold, etc? I've had the Jeep since 98, and would like to keep it, but realistically need to look at better mpg vehicles if I'm dreaming of getting atleast 20 mpg.
Thanks, - Bill -

 

You drive a Jeep, they are not mpg vehicles. Drive 45mph...

 

Give her a complete tuneup, changing all plugs, filters, fresh oil in the engine and the axles. Watch your tire pressure. Install new O2 sensors. I have heard of people tinkering with the injectors. Something about higher atomization rates..?..

20 mpg is a sure stretch for V8 jeep! LOL...

 

The key to better fuel mileage is in your right foot. No manifold or chip is going to improve your mileage.

 

I can get 20 from my 4.0 on the flat highways of Florida, but even here I don't think you would get close to that in a 5.9. I would say you're doing pretty well for the motor that you have. Sorry to burst your bubble, but if this helps, do the math and see how much you would really save with an additional 5 mpg. Unless you're racking up a ton of miles each month, the difference is very small. I nearly sold my WJ to go back to a Honda last summer until I broke out the calculator and learned that if I went from my current average of 17 mpg up to 25 mpg in a Accord I would only save around $50 per month at about 800 miles a month (granted I'm not racking up a ton of miles). No thanks, I'll gladly pay that to drive what I want to drive. Thankfully I'm at a point in life being debt free and having a great job that I can enjoy some extra things, but there was a time when I was burning up the roads to finish college and work 3 jobs while paying a mortgage and supporting a wife and 2 children, and I had to sell a built XJ to buy an Accord. If you're in that spot, sell the Jeep and do what must be done to get through this stage in life.

 

You can get better MPG than what your getting. My 5.2 gets 22-25 mpg.

Taken 4th of July 2011. 205 miles one way. 21 mpg according to overhead. Hand calculated was 22.6. It took 9.1 gallons of gas to top off. This video was taken with the ZJ not running and the ignition on. Thats why it shows 0 for eco.

 

I've been really really trying to baby my 04 overland. This is the best I can get out of my 4.7ho. That's after 3days and about 110 miles of driving

 

how about installing an LP Gas system?? I have one on my Xj 97' and it really helps, btw i'm trying to buy one of those 5.9 limited and if I get it, I will install one of these LP gas systems

 

Prius.

 

This is me babying my 4.7 2001 on 31s that's with about 170mikes on the tank and I have a little less then 1/4th left I drive 60-78 miles a day

 

Wow im lucky to get 12-15...lol...would a 242 tc swap help his & my mpg problem?

 

I have a 98 5.9 limited, only had it a few months and have been working on that same problem. so far I am using a 5.2 cpu (so I don't need to use premium gas), an mp-1 intake and a 52 mm throtlebody (got them really CHEEP) W/ cruz set @ 55 on flat ground over head shows 20 to 24 @ 60 19 to 22. I want to improve my exhaust system I think there is a LOT of room for improvement there. My feeling is headers and a good exhaust system I should be able to get 20+++ @ 65.

 

I want a 242 tcase really bad but the junk yards have none for the v8 and online there really hard to find and when I did it was 600 bucks little out there

 

Anyone replace their single exhaust on the 5.9?

I would have to believe that the single exhaust robs the jeep of better mpg and additional hp. Curious to know if someone has already done it, and how was the outcome?

 

You're grasping for straws here. You drive a Jeep with a large V-8 engine designed 30yrs ago. What do you expect? You obviously own it outright, so no payment. And then throwing $$ at it with aftermarket parts tyring to improve mpg is a waste of time. I would do a complete tune-up if it's due,and your right foot will dictate your mileage.