So my brother has a 15jku and has talked me into buy a jeep! So I bought myself a 1998 keep Cherokee with 136 on the clock!
Bought it about a week ago and have already changed the oil to castrol gtx high mileage synthetic blend, changes the spark plugs to new champions, and replaced the o2 heater sensor (cel). Have ordered my re 3.t lift with bilsteins and bought 31 bgf km2 all terrains but my question is the car runs great! But can't get no better than 14 mpg!! I read that people here he around 20 mpg while lifted and 31s! I am stock and have new oil, new plugs not lifted and stock tires! ( two issues I have also are when car is cold won't turn on the First time but always the second! And the cat is about a year old and rattles) so what could be causing my mpg to be so bad? Thanks

 

Chances are, it's not just ONE part or thing causing the mpg. It's a load of them. As time slowly goes by, change one thing here, one thing there... it not new, and although we don't generally get above 18 mpg, it's a heavy, metal, safe, reliable, and FUN jeep to drive.

Good luck, have fun, and at only 136000, you're likely to have that Cherokee for years to come.

Congrats! And welcome to the addiction!

 

I very much doubt such claims. In good running condition, a stocker should get a combined mileage in the 18-20 range, with a good driver.

But still, 14 MPG is really bad, and if that's an accurate MPG calculation, it means you have a problem.

As already mentioned, could be many things. A vacuum leak is a prime suspect.

However, the first thing to check is your method of calculating it. There is only one correct method. Take the miles driven (as measured by an accurate odometer) divided by the number of gallons as measured by the gas pump when you fill up.

If your method involves the gas gauge in any way, you actually have no clue what your mileage is. The gas gauge is nowhere near accurate enough for calculating mileage.

I mention this because I see a lot of kids on here who think they can use the gas gauge to figure gas mileage, and it's just not going to work. They are stubbornly sure it's accurate, and they run around like chickens with their heads cut off, chasing problems that don't really exist, or bragging about mileage they aren't really getting.

So, make sure your odometer is correct, and that you are using the correct method of calculating it.

 

Well stated. Mark, you need to "can" a version of this. I'd use it.

 

What Cruiser said!


Even 31" tires will cause a slight decrease in mpg's with the stock 3.55 gears.

 

and again!

So many car forums have this mpg question going on. There's only one way.
Fill the tank until you can see fuel in the pipe. Zero the odometer. Drive as far as you like, but preferably until you're nearly out of fuel. Fill the tank again up to the same place as last time. Check the odometer.
NOW you've got a basis for calculation.
Repeat as necessary.

 

Better yet, if you have an Android smartphone, use aCar. Even the free version is terrific.

Track all your maintenance, fluid changes, see the real story.


I'm an engineer, and I have seen a lot of software. All the usual stuff any computer user sees, plus a lot of expensive specialty engineering software, and this is among the top 5 I have ever seen for just doing exactly what it needs to do, and doing it simply and well.

 

hmmm, I'm going to have a look at that. Thanks!

 

Vaccum leaks can cause this? I notice when I bought it the previous owner just removed the air box and left the elbow and threw a filter on it and I noticed the hose that connects to the intake from the valve cover just hangs and I see a lot of cracked lines as well,

 

And yes I am tracking them by puttin 17 gal exactly every time I fuel up and resetting the trip!

 

Yes, sir! Probably the #1 cause, perhaps? That or a bad O2 sensor.

Here's what happens:

Excess air gets into the intake, causing a lean condition. The o2 sensor sees too much oxygen in the exhaust, so it tells the computer to dump more fuel into the engine. The thing runs, but you get really bad gas mileage. Fouls the plugs, too, eventually, so you get misfires.

A crack in the exhaust can do the same thing, too.

Fix any vacuum leaks, then see where you stand. There might be more than one problem, but I'd start there based on what you said about the cracks.

 

Your driving a 4x4 brick anything over 10mpg is a good day to me.The ones saying 15 to 20 mpg are stock probably a stick and drive like a old lady.

 

15-16 in town, 20 or so on the highway. Totally stock.

 

If you are getting 10MPG on a stock rig, you have a problem with your engine.

 

I always filled up till the auto shut off clicked the first time, shut the pump off and pulled the spout out of the filler neck. I have 164,000 on mine and drive city miles to and from work and get 16.3 with stock wheels. Weekends are a different story however as I seem to get around 13.