gas guage says losing gas quickly (guage is correct...now a mileage problem)

[RunnerUp]

Try running it until its about to run out of gas, fill up, should be VERY close to 18.5 gallons.

no matter how close to E i get i have NEVER filled up more than 17.5 gallons... even the time i ran my truck clear out of gas it didnt fill up to 18.5, does yours? is mine really that dented?

[YotaFun]

Try running it until its about to run out of gas, fill up, should be VERY close to 18.5 gallons.

no matter how close to E i get i have NEVER filled up more than 17.5 gallons... even the time i ran my truck clear out of gas it didnt fill up to 18.5, does yours? is mine really that dented?

Probably.
I about coasted a few weeks ago into the station and it was 18 for me
(i have a slight dent too...)

[cobradcab6]

ok so i filled up with gas when the gauge said i had 3/4 of a tank...... that would mean it should take about 4.5 gallons if the gauge was correct. i had only driven about 40 miles so it should have only taken just over 2 gallons to fill up. well it took about 4.5 gallons so that means my gauge is fine and something else is causing my gas mileage to go from 17 down to about 9. so now the hunt is on to find out why my mileage would be cut in half all of a sudden.

[Tankota]

Wow that pretty drastic. Does it still have all the power you think it should have.

I wonder if it could be a fuel leak. The hard thing about gasoline leaks is that they usually evaporate before you can find it.

[cobradcab6]

yeah everything i've checked around the tank and the fill hose all look sealed and dry so i don't see or smell any signs of a leak. i haven't noticed any power loss either, just the mpg

[04 Rocko Taco]

If there is NO power loss, then that in itself almost points to a leak somewhere, just about anything that will cause your mileage to vut that drastically also would cut power drastically.

As far as not finding any leaks though.... a few other easy things to check...
fuel filter? (also a known place for leaks)
plugs/wires?
coils?
tire pressure? (although this would have to be WAY off I can run with 35 psi, or 9 psi, and still be within 4-5 mpg)

[bamachem]

let me take a wild guess... 120k to 140k miles, probably a 00/01?

correct?

rear O2 sensor would be my guess. i had one going south and was getting 13MPG with no check engine light. replaced it w/ a bosch from URD and MPG's jumped back up to 18 or so. you can check it before you drop $100 on a new one too...

[cobradcab6]

2003....... and not past 100k yet

[04 Rocko Taco]

I did have a convo with Jesse about the O2's Andy. Sounds like it may be the culprit. Link to the testing procedures? I am going to help replace if it seems bad.

[bamachem]

there's a procedure in the FSM - which i don't have in front of me.

make sure to get the replacement from URD, and if you do, then one phone call to them would give you the tech help you'd need to diagnose a bad one too...