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Improving Mileage on Lifted '99 XJ

What is the axle gear ratio ? What size tires ? If you did not change the t-case speedo gear, be sure to adjust the gas mileage for larger than stock tires.

Really about the only way to improve the gas mileage of your brick shaped 4x4 is to carry less weight, and to slow down. Keeping up with the routine maintence tune-ups, checking that the exhaust manifold is not cracked, and OBD sensor replacment will prevent the mpg's from slipping.

I have +1500 miles and an average 16.7 MPG's on 5.5" of lift, AW-4, 3.55 gears and 31's.
 
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I get like 12 with an AW4, 4.88's, and 35's running 4.5" of lift. Best thing I ever did for fuel economy was put it on a trailer behind my truck. Get between 14 and 16 that way depending on the terrain I'm towing through and how fast I want to get up the hills.
 
I've got a set of those injectors I took out when I built my stroker. They helped a "little". After my stroker build I was down to about 11mpg with 27# injectors, with a ECU tune and some 24# injevtors I'm now getting 16.5mpg.
 
What is the axle gear ratio ? What size tires ? If you did not change the t-case speedo gear, be sure to adjust the mileage for larger than stock tires.

Ok ... correcting for the 31" tires, I got 15.5 mpg. I didn't even think about the fact that I hadn't changed out the speedo gear and that they would affect the calculation.

My exhaust is pretty much toast (20 years old and never had a part replaced).

I have the stock gears (whatever came with the Upcountry Suspension Package with the integrated rear lockers). I want to stay with the stock gears, since I plan on putting in a new stroker once I move back to the U.S.
 
I used a set of 4 hole injectors from K Suspension. They've worked great and the installation video on their site was spot-on.
 
I was getting around 19-20 MPG doing 70mph on the highway on 31s with about 3" of lift and stock gears. Id been around 13-15 til i swappped out my bad O2 sensors and worn out spark plugs.

i now get about 14-17 MPG on 33s, 4.56 and about 6" of lift.
 
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on my last road trip, all highway on mostly interstate 5, not in the mountains, I got 16 mpg at 70 to 75 mph. 33 inch offroad tires, raised 5 inches, 4.11 gears auto tranny. 1990 cherokee, six cylinder. speedo is corrected for tires, gearing.
 
I get about 16mpg with ax15 np231 no lift 3.07 gearing 33" tires 80mph. I haven't adjusted the Speedo gearing but I have done the math so I know how fast I'm actually going.
 
Tim in MN said
"
Really about the only way to improve the gas mileage of your brick shaped 4x4 is to carry less weight, and to slow down"
So check your driving habits
ALSO
An exhaust leak at the head/manifold will kill your mileage!!
This is B/C anywhere that exhaust leaks out also allows oxygen in
This makes the O2 sensor think the engine is running lean
Then the system adds fuel-makes it rich This of course reduces MPG
 
1990, 4.0, AW4, stock gears, 4" lift, 17.5 MPG.

I'm running a "nominal" 32-inch tire: P255/70R18. Yup, JK wheels: Less rubber, less rotating mass, less parasitic loss. If you want squishy sidewalls, pay the price.

Y'all look at MPH, I look at RPM. I cruise 65 MPH at 2500 RPM, right where the torque curve starts twisting the wheels. From 2500 to 3000 RPM, the 'ol 4.0 eats the highway. When my cruise RPM gets above 3000 RPM, I start losing efficiency. My last trip from Denver to Ft. Collins, and back, netted 16.5 MPG.

Moral of the story: It takes less throttle to maintain higher RPM/Torque.
 
lifted and MPG shouldn't be in the same sentence
 
I used a set of 4 hole injectors from K Suspension. They've worked great and the installation video on their site was spot-on.


What does "worked great" mean......per the OP's question, are you implying that you measured an MPG improvement by upgrading to 4 hole injectors from K Suspension? :dunno:
 
I'd kill for yalls mileage. Stock 95 XJ (upcountry height) w/235s and I'm averaging 13 mpg lol.

Cracked header replacement is scheduled for this weekend.

Sent from my SM-G892A using Tapatalk
 
I'd kill for yalls mileage. Stock 95 XJ (upcountry height) w/235s and I'm averaging 13 mpg lol.

Cracked header replacement is scheduled for this weekend.

Sent from my SM-G892A using Tapatalk

Yes, you have some work to do!

If you have not already replaced the Oxygen Sensor, replacing it with the manifold is about as easy as that job gets.
 
Surprisingly no one has mentioned tire pressure. Whats best for wear isn't usually best for gas mileage, I usually add 2-3psi for long road trips.
 
Yes, you have some work to do!

If you have not already replaced the Oxygen Sensor, replacing it with the manifold is about as easy as that job gets.

Yeah it's been replaced I've been hitting the manifold bolts for about a week now daily with PB Blaster so hopefully (fingers crossed) all those bolts come out easy enough.
 
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