Pimp out my Mileage!

[Naval XJ]

I am shipping out for the Navy May 9th, and as a early b-day gift giving my brother my '99 Jeep XJ. Sadly, he's not into the offroading world like I am, so I decided i'm going to make it more fuel efficient for him.
I need to know what will do that, I know a better intake and exhaust system, but is there anything else like performance chips or something i should know about?

 

[bob91yj]

Congrats on joining the Navy!

Skinny tires, fresh fluids and a tune up, remove the roof rack if it has one. Don't waste your $$$ on do-dads that make ridiculous claims...any gain realized will not be cost effective, IMO. No fancy spark plugs either. I run Champion Truck plugs in all three of mine. I'm a dealership service writer, seen numerous 4.0L's with misfire codes after owners have installed platinum, or specialty plugs.

The 4.0L is a great engine for a tractor, not good for much else. Short of stroking it, roller rockers, port/polish intake/exhaust, the engine is what it is, bolt on parts will be some of the most expensive horsepower ever.

 

[Root Moose]

The 4.0L is a great engine for a tractor, not good for much else. Short of stroking it, roller rockers, port/polish intake/exhaust, the engine is what it is, bolt on parts will be some of the most expensive horsepower ever.

Quoted for truth.

 

[mac]

X2 :smiley_drive:

mac

 

[Purple People Eater]

Tell him to drive barefoot. :victory:

 

[Naval XJ]

Tell him to drive barefoot. :victory:

lol, I always drive barefoot, how does that help?

 

[NOMADIC_LJ]

Sell the Jeep and buy an econo box.

Seriously though you are fighting an uphill battle and there is very little if anything you can do to make it more fuel effecient.

 

[Root Moose]

lol, I always drive barefoot, how does that help?

Faster lap times for the same amount of fuel.

 

[Coastie]

Leave it with the lift and tires and he will become "into" offroading and then he won't care about the mileage

 

[Naval XJ]

Faster lap times for the same amount of fuel.

Oh, so you guys are just messing around with me?

Leave it with the lift and tires and he will become "into" offroading and then he won't care about the mileage

Good idea, I'll leave it parked in the middle of some offroading spot for him to get, he'll have to offroad to get it home!


Neither of us want an eco-box, just think if there's a zombie invasion! The only vehicles you'll see driving around are gonna be offroad vehicles! Sure, that Prius gets 45MPG, but it won't get 1MPG if all the roads are covered with dead bodies and zombies! And don't say that's not a valid point, zombies are very valid!:jump:

 

[proto]

The problem with trying to increase fuel mileage is there's usually not just one thing to fix. That said, the single biggest improvement I ever got was switching tires on my old 4x4 Blazer. On advice from some folks in one of the tow-rig forums, I replaced my M/T-style tires with BFG Radial Long Trail Tours (the 'Tour' part is important).

Mileage jumped from about 14 (highway) to 17.5 and stayed there (measured consistently over several dozen tankfulls). All of a sudden my gas bill was 80% of what it was before the switch. Of course, the changeover cost about $600 for four tires plus a spare.

You could do some fancy payback analysis and figure how many miles you'd have to cover before the fuel savings pay for the tires -- but I figure I would have needed new tires anyway, so it was a no-brainer.

Do I need to say YMMV?

 

[4Rescue]

Sell the Jeep and buy an econo box.

Seriously though you are fighting an uphill battle and there is very little if anything you can do to make it more fuel effecient.

x2...

There is literaly NOTHING you can do to make these motors more fuel efficient... All of them I have had were just plain fuel thristy. Hard to swallow (no pun intended) when you have an INLINE motor spinning at 1500-2k on the freeway for mile after mile and it's still not getting over 15mpg...

Cheers

Dave

 

[Root Moose]

FWIW, when my 2001 was stock I would consistently get ~20-22 mpg (US gal) on the highway provided I kept the speed under 110 km/h and used the cruise control. This was on the relatively flat four lane highways of Ontario.

When I added the ARB bull bar I lost ~1-2 mpg.

With 5" of lift. Well, yeah.

 

[wADVr]

Having everything working properly is the best thing you can do to regain lost mileage. Im not sure what mods you have or if its stock but simple tune up parts, an alignment and fluid change ect have been the most beneficial for me. If its lifted with bigger tires making sure you have the proper gearing it hands down the best thing you can to. 31s need 4.10s, 33s need 4.56s, and 35s, 4.88s.(assuming 4 sp auto equiped) Overgearing the XJ from stock helps quite a bit even on freeway trips and helps cope with the heavier tires, racks, equipment ect.