90-110 Miles, one FULL TANK!

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sohllis

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Joined
Mar 27, 2018
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36
Location
Altamonte Springs, FL, USA
I've been reading around the forums to see how much miles folks are getting on a full tank and it seems the average is around 180-210. Well! I'm significantly below that threshold and averaging 90-110 on one tank.

I don't beat on it and always shift around 2100 RPMs. It IS on a lift but I'm not sure how big the tires are, could be 33s. I am getting a CEL for bad cats which I plan on swapping out this week but I don't think a pair of bad cats should significantly kill gas to this point. I don't know if the previous owner regeared but my TJ does seem pretty weak in 5th and 6th gear. Sometimes feels like a Prius despite sounding like it's about to fall apart (got to love all the noises)

Any thoughts?

Be nice. I'm a first time Jeep owner and I'm fully aware our rigs don't get good gas mileage but 90 to 110 miles on a single tank? I may as well be driving M88A2 Hercules
 
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Unbelievably ridiculous if you only get 110 miles from a full tank. As if you stayed on 3rd gear on the highway.
That is a serious concern if I were you. Like balfred said, maybe it is a cat problem.
 
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Even with a 15 gal tank, that's well under 10 mpg.....about the worst I've heard.

If your getting a code for the cats then definitely replace them.

Look at the tire sidewall for your tire size.
It's not uncommon to be under geared which also effects gas mileage.
 
It could be cats, but it also sounds like you're geared way too tall for those tires, and your speedo,and therefore mileage isn't accurate.
 
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Going by just the gas gauge can make you believe you're getting really poor mileage since the TJ's gas gauge is notorious for dropping fast and saying you're nearly out of gas when you in reality have much more gas in the tank than the gauge is indicating.

The ONLY ONLY ONLY way you can tell what your mpg is is to fill up the tank and note the mileage. Or reset the trip odometer to zero when you refill. Then when you refill the tank again, divide the number of miles driven by the number of gallons it took to refill it which is the only way to accurately know the mpg.

Please don't feel insulted if you already knew that procedure, plenty of smart people just go by the gas gauge because they trust the gauge... which you can't when you want to know the real mpg.
 
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Jerry is right. I never go off the gas gauge. I always reset my trip odometer every time I fill up. If I do that, I have a pretty good idea of how far I can go before I need to fill up again.

The fuel gauge on TJs is indeed notoriously inaccurate.
 
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I found out how off the gas gauge was by paying attention how much gas it took to fill up at the gas station. I knew I have a 19 gallon take, and once it took about 15 gallons to fill up.

I figure I have about 3 gallons in the tank once I get in the red.

Once I figured that out, I always pay attention how much fuel I buy. Doing this, and I have found that I haven’t had to do the fuel spill fix either.
 
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lovemachine said:
I found out how off the gas gauge was by paying attention how much gas it took to fill up at the gas station. I knew I have a 19 gallon take, and once it took about 15 gallons to fill up.

I figure I have about 3 gallons in the tank once I get in the red.

Once I figured that out, I always pay attention how much fuel I buy. Doing this, and I have found that I haven’t had to do the fuel spill fix either.
Click to expand...
Exact same here. I pump the same amount each time haha
 
So I replaced the pre-cats, the third cat, and got a whole new muffler system from banks. I just filled her up yesterday so I'll track the amount of miles I get on this full tank and follow Jerry's steps. After replacing the whole exhaust system, it feels more responsive in 5th gear but still feels a little weak and I still feel there is opportunity in 6th gear. It holds a lot better but I know it shouldn't feel like it's struggling to maintain x speed and certain RPMs in those gears.

I'm still throwing CEL for P0456 and P0457 which was the whole issue with bad cats or O2 sensors. I'm going to reset ECU in a few
 
sohllis said:
So I replaced the pre-cats, the third cat, and got a whole new muffler system from banks. I just filled her up yesterday so I'll track the amount of miles I get on this full tank and follow Jerry's steps. After replacing the whole exhaust system, it feels more responsive in 5th gear but still feels a little weak and I still feel there is opportunity in 6th gear. It holds a lot better but I know it shouldn't feel like it's struggling to maintain x speed and certain RPMs in those gears.

I'm still throwing CEL for P0456 and P0457 which was the whole issue with bad cats or O2 sensors. I'm going to reset ECU in a few
Click to expand...

Try clearing the engine codes with an OBDII scanner first and see if that works.

I hope you used NGK sensors for the O2 sensors too...
 
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