so i filled up my 3.8L mustang today right before work. its a 31mile drive to work and when i got here, 1/4 tank was gone. there doesn't seem to be a leak. i wasn't driving with the AC on, barely ever do. not really much extra weight in the car except for me/subs. tire pressure is all good, no CEL either.

any ideas or things to check first?

 

Geeze, after i fill, it takes about 35-40 miles to get to the "Full" mark.

 

yeah i dunno what the hell it is. like since thursday ive been gettin **** gas mileage. i was full on thurs and empty by this morning and didnt drive much over the weekend.

 

how many miles do you have on your car?

 

just over 70k

 

i was talking with my stepdad when i got home. it slipped my mind that about a week ago when i was getting gas the pump didnt shut off and overfilled my tank. he said theres some emissions part or something that was probably damaged but i didnt catch what he said. can anyone elaborate?

 

That wouldn't effect it since I've over filled once (since my gas gauge read lower than what was actually in the tank) so I filled until gas came out. Still getting the same mileage. Where did you go to fill up? Some of the no-name guys use garbage for gas. Also, is the gas gauge staying at the same spot? Sometimes when you drive/park on hills, it'll read lower/higher than what you actually have.

 

the fuel gauge reads consistently. i forget which station i went to today but the end of last week it was a Thorntons which i usually go to.

 

maybe your gauge is just messed up. Mine stays on full for 65 miles then it runs down the rest of the gauge pretty quick. I still get about 250 to a tank though, so all is good.

 

gauge seems to be working fine. it doesnt stay on full for a long time, thats for sure because i noticed it dropping faster than usual today. when it gets low and "low fuel" light comes on too.

 

fill it to the top...drive til the fuel light comes on...and fill up again and figure out your gas mileage for your tank. See how many mpg your getting.

 

I was having recent gas mileage problem related to sticking calipers. I honestly think I was losing near 50 miles a tank. I'm sure you would of noticed something with the calipers if they were acting up though.

 

Hey there,

I live in MIA which is usually ALWAYS freakin' hot so I am always running the A/C...day and night!

I fill up from extreme empty (13.xx gallons), I work 20 miles away from home, that's 40 a day and the traffic usually takes me 1 hour each way.

I get 200 miles per tank, I usually count 50 miles per quarter...If I am at 100 miles and half a tank I know I am doing good with my mileage. If I am lucky I can squeez 220 miles but that's hitting the "E" pretty low!

I have 112k miles on a 2000 mustang.

ps- I just seafoamed my car today so lets see if that makes a difference in mileage.

good luck,

ceez

 

wow, you should be getting better gas mileage. I used to get 260 miles a tank in my Mach 1 and that was sitting in traffic. On the freeway I'd get around 300 miles.

Could it be the injectors clogged or something like that?

 

i was told it could be the injectors. im gonna pickup some lucas' fuel injector cleaner tonight on the way home. it kinda seems to be getting better. i can get 240mi/tank. no idea how you got 300 in the mach1 and im in a 3.8. i guess the 3.8 doesnt get as good fuel economy. even my stepdad gets better mileage in his modded GT. they took it to michigan on a road trip and averaged 24mpg

 

Hell, I got 300 miles to 3/4 of tank giving me 30 mpg on my GT. Then again, everyone one of those 300 miles was done on open highway.

 

i drive on the highway everyday. my commute is ~60mi roundtrip and id say 50 of it is highway

 

dang im lucky to get 275 out of a tank with my GT. Putting the cams in is only gonna make it worse too right?

 

well, the 300 miles was on open highway so it wasn't a common thing for me. I'm pretty sure your car is having some sort of issue because the 3.8 should be getting more than 240 miles out of a tank of gas. You also might want to monitor your driving style. You might be a lead foot and don't even realize it!

 

so here's the current status...

im still getting ~240mi per tank which is what i usually get.

when i fill up my tank, the needle doesnt go as far to the right as it should, it sits just below the line for Full. if i tap the plastic over the fuel gauge it sputters around a little bit. it was also sputtering around during normal driving as well. could this be a faulty fuel gauge or something else too?

 

have you had your car dyno tuned recently? Maybe the jacked something up. Go get it tuned at a shop, dyno tune.

 

no, dyno tune. no real need, i dont really have any performance mods done to it other than a cold air intake.

 

anybody know if a CAI put on incorrectly/not sealed can mess up gas mileage like that? Or you did you clean off your MAF sensor when you put it back on? Spray it with some brake cleaner, let it dry, then throw it back on. Have you dont that? Made sure the intake is torqued down good?

 

ive checked the intake and everything its sealed properly, but the MAF is something i didnt do, i will have to give that a look

 

something still sounds awry to me in regards to the fuel tank/gauge because when i filled it last night, my buddy and i were in the car and looked at the gauge and it definitely wasn't on full. when my Low Fuel light came on yesterday it still said i had about 1/8 tank left. then when i turned the car off for about 15 mins and turned it back on the gauge was on the red line for Empty

 

check your sensors. You have a programmer? maybe it will tell you that the sensors are bad.

 

might want to change your fuel filter as well.

 

As an update, I seafoamed my engine last week and filled up the tank. for the first time ever I was able to drive 235 miles for a full tank!!! Amazing, lets see what happens with the 2nd fill up.

 

only 235 with a v6? thats pretty low.

 

does anyone know at what point the Low Fuel light comes on? like how many gallons are left in the tank at that point?

when i fill up when it says low fuel its been 13.5-14 gallons to fill, but i read online that the tank capacity is 15.5 gal. so it seems like it comes on with 2 gallons in the tank. im trying to get an accurate MPG. if i calculate it based on using 13.5 gallons of gas on 240 miles, thats 17.7mpg, which sucks

gonna check fuel filter and the fuel gauge tonight. also, i pulled one spark plug and it was brown and had a sweet smell. anyone know what that means? i doubt theyve ever been replaced so im probly gonna do that too