96 keep Cherokee sport with 164k on the clock aw4 4x4. Previous owner said he swapped in a 96 engine with 75kish and I swapped another aw4 with 70k.

I'm running 31s on a 1 inch lift and I'm getting under mpg. I filled up my tank completely a couple days ago and after about 130 miles (if even that much) my gas light popped up and I drove it to about 1/8 a tank left. This can't be normal, ive already seafoamed it and did an oil change about 1000 miles ago.

Help me out? This is seriously killing my wallet

 

99 engine* if that matters

 

First, you MUST calculate gas mileage. Miles driven divided by gallons consumed. Trying to figure your gas mileage by estimating miles to a tank is not accurate and confusing to boot. You need at least three calculated samples before making any assumptions. And factor for the 31s even though it isn't that much.

 

Definitely factor in the odometer being off from the bigger tires. Mine is off by 10 percent and i'm only running 30s. So for every 10 miles on the odo i add an other mile.

You can see how far off your odometer is by watching the mile markers on the side of the road and comparing them to your odometer. In my case, for every mile marker i passed my odometer would only move 9/10ths of a mile.

 

^x2

 

I think the previous owner fixed the speedo/odometer. I compared my speedometer to my gps speed and it's dead set correctly. I'm going to fix my exhaust leak and see if it helps. If not I guess I'm going to change my o2 sensor and clean all my other sensors and throttle body etcetcetc

 

It's never a bad idea for anyone to check the condition of the tube from the TB to the MAP sensor up there on the firewall, and that is is giving good vacuum to the map. (with your finger). The less vacuum the map gets, the more fuel it will dump.

 

Do you actually calculate your mileage? Typically I drive the exact same route to and from work, over and over. The conditions, distance, traffic speed, etc. are usually very close to identical. I fill up, re-set the odometer and note the mileage and date in a little notebook. Next time I fill up, I fill it exactly the same (usually at the same gas station, even), then note the gallons pumped and divide the miles driven by the gallons pumped. My '95 XJ (4.0L, AW-4, NP231) gets about 14.4 miles/gallon if I keep my foot out of the accelerator, run the speed limit and keep the tires aired up to 50 p.s.i.

I recently aired down to 40. I'm watching to see if the mileage drops, and I'm betting it will. At 32 p.s.i. it gets about 13.5. An increase of 0.9 mpg isn't much, but it's about $5.04 per fill up, and I fill up about 60 times a year, so that is approximately $300 a year. All by running an extra 18 p.s.i. in my tires. That's three hundred bucks I can spent on something else besides giving it to the ******* gasoline companies.

Of course, if the extra air caused handling problems (in the rain, say) and caused me to have a wreck, that would be false economy. It rides a little harsh with the tires aired up tight, but it seems to handle okay even on wet pavement.

 

Cleaned my throttle body and all associated sensors as well as changing my upstream o2 sensor and My xj feels as smooth as ever and has increased in fuel efficiency.