Wow that is really bad. I just filled mine up at 245 miles and still had about a 1/4 tank left. Took around 13 gallons to fill up from there. And yes my speedo has been verified by 3 different gps units. It is dead on.

 

Everything is stock running 235 tires and everything is accurate. I should mention this is with ac too. And from what I calculated because I topped at the filler neck. Yes I know that's bad to do but I wanted to make sure and that was about 18.9 gallons back to its spot again. So calculating the mpg I got 10 mpg.

 

Yeah, actually 9.77 MPG. Something's not right!

Are you seeing any soot around the tailpipe?

 

Not from what i see but this week i am doing a well needed tune up and ill pull the spark plugs and see what exactly its doing.... Also im highly suspecting my cat is a problem too since its still factory. But hey! i finally got a job to actually do well needed maintenance items now! Any recommendations on spark plugs, wires, rotor and caps? I was told to stay away from the tune up kits from auto part stores as they arent that good.

 

Also i did swap out the iac a while back because one of my home made plugs blew out and had a vacuum leak so after i fixed it it rev hangs slightly still so i may swap my old iac back in and make sure the seal is good and then reset the computer and relearn everything after the tune up just to eliminate any stupid issues. I made a thread about that rev hang before but never solved it yet tho it does it randomly.

 

Here is a list of ignition parts that were suggested at one time.
NAPA:
rotor-ECH MO031
cap-ECH MO030
wires-BEL700444

Get NGK ZFR5N plugs where you want.

 

alright thanks!

 

No problem.

 

from a full tank? that's terrible. mine will go 185+ to a half tank. it's averaging 21 mpg. it's on what i call its ethanol tank now so it's getting 12-14 mpg, which is still 30%+ better than yours. i put 7 gal e85 in it before filling it with gas. i do that once a month. it was getting consistent 19 until i did a full frontal tune up and some exhaust work. runs so much better now.

 

yeah thats what i suspect half of my problems lay is within the exhaust system and ignition system. I was planning to get a full exhaust system with hangers and all from rock auto because im sure using metal coat hangers isnt a good way to approach a hanging exhaust. And talking with the previous owner he said the last tune up was from 2006 so may need a tune up as well..... Also kinda embarrassing when you go to start it up and it was at that perfect point to backfire out of the throttle body and blow all the intake plugs out UGH. So needs work lol. And yep that is my current gripe because 185 miles out of a full tank of gas is slightly annoying and hurtful to the wallet lol. But also this has been with ac the entire time from when i filled up. I wish i can run it without the ac and see if maybe my ac system is putting alot of load on my engine but yeah heat strokes.....

 

Ok well ill wait to update in winter but i think my ac is a main concern here. Its been cooler in florida and using my ac less and less and noticing my mileage is going back up i mean right now i have a quarter tank but i went 210 miles this time and not running out of gas. Tho i never took note or tried it but i swear before without ac at all before i got it charged i almost ticked 300 miles on a single tank of gas and that was even with a quarter tank left. Does this mean my ac system is really putting a load on my engine? It is ice cold and seems to work well and doesnt seem to strain the engine out when it engages. Ill get better results when i get to a point where i can use no ac on an entire tank of gas i did do a tune up and wow it made a difference in pickup speed and all and even better mileage as well but still bad. When i get a new exhaust system ill get even better results too.... But Is there anything i can do to my ac compressor to maybe possibly free it up? Tis a mystery this issue and it makes my wallet bite my hand when i get near it.

 

hmmmmmmm come to think of it i wonder if my belt is to tight. Maybe ill loosen it up a wee bit and see if that will help as well.

 

The AC shouldn't do too much to your mileage, maybe 1 MPG.

 

You might have a bad O2 sensor making it run rich. Yea, yea; OBD2 is supposed to tell you it's bad but I have first hand experiences that state otherwise. If the O2 is reading wrong but still putting something out the system might not trigger a fault.

 

I had a bad O2 sensor and my XJ was burning gas like nobody's business. At one time I burned a whole tank on a 36 mile trail ride that took a good part of one day. My buddies wrangler also with a 4.0 only used 1/4 of a tank that day.