98 grand prix gt uses excessive fuel

[bcampbell]

Does anyone have any idea why my car would be SUCKING down gas? Gas is so high right now it's killing me. It's using twice as much and I'm not going any farther than I ever have.

[BNaylor]

Originally Posted by bcampbell

Does anyone have any idea why my car would be SUCKING down gas? Gas is so high right now it's killing me. It's using twice as much and I'm not going any farther than I ever have.

What are you currently getting in city or highway or combined mileage?

A lot of factors will affect gas mileage. Driving habit/style, tire pressure, old spark plugs, worn plug wires, air filter, PCV valve, etc.

I've even seen dirty/carboned up 02 sensors (front and rear) cause reduced mileage. A clogged CAT convertor could do the same, especially when mileage on the car is over 80K miles.




Thrasher CAI, DHP v1.0 PCM,
3.25 SC pulley, CAIT GMAF, Hi-Flow CAT,
u-bend delete, 160 TS, ZZP Stage 1 TB,
TB spacer, MSD 8.5mm wires, Autolite 104s,
Goodyear Gatorback Serp. & SC Belt,
Nitto NT555R Drag Radials

[mike561]

yea i noticed my gp is also a real guzzler too, i will look into doing those things though, if i could i'd get on the highway, nail it full speed and wach the gas guage slowly but surely go to empty, prolly within a really short amout of time too.

[GTP Dad]

Everything that Bob posted will affect your car's mileage. Driving habits are the biggest cause of decreased fuel mileage. If it is mechanical then the items stated if replaced should help somewhat. I can get 28 mpg highway on my 97 GTP if my son drives it he can only get about 19 on average. He likes the supercharger, I only use it when I need it.

[regalfriend]

First thing i would do is what Bnaylor(Bob) suggested. A combination of loww air pressure, a slightly clogged air filter, and old spark plugs or wires can greatly reduce your milage...My friend complained of the same problem and noticed his air filter was clogged and his tires were a little low and his trunk was full of crap. We corrected all of these problems and increased his milage by 8 MPG.This was a 1991 Toyota Camry though

[bcampbell]

i will say, i don't drive bad. and even if i do (ha ha), it's not any DIFFERENT than i've ever driven. i really don't get on it too much but i was told that i should once in a while. and really the only reason i don't is because of the gas. i'm going to try all those things. it might be a little of everything. i know it was getting hot for a while if i would sit for example in line at wendy's, and then cool back down once i took off. we took the garden hose to the radiator and cleaned it out real good and now it's a lot better so i wouldn't be surprised if it's just kinda dirty.

[jessep28]

Mine was only getting 18-20 in mostly city driving with the A/C on during our heat spell here in NE. I don't gun the car either or drive it like I stole the thing.

However, that could be attributed to bad plugs and wires causing my random misfire problem, so I just had that fixed.

Learned during that repair that my fuel filter was original at 45 k (yikes!) and air filter was dirty. Kudos to the dealer for not doing that during the turnaround before I bought it, so I just did all that this weekend. But it was my fault for not checking.

I filled up last night and milage was 21.3...not bad but not great either. But this will be my first full tank sicne I fixed all that stuff though.

Sorry for babbling.

[dmasjz45]

if it started using twice as much then it might be more serious of a problem such as a gas leak, have you noticed any spills on your driveway or the smell of gas when driving or after parking? any smell coming from the engine bay? it would take quite a huge combination of problems to change mileage from 20 to 10, regarding its a deffinate loss in gas mileage. i usually get 25-27 mpg on my gt, but shes in great condition all around with 86k miles, and i even abuse her sometimes too. of course thats a combination of highway/city but i do more city. im sure it attributes to all the people i piss off when i coast from 40 to 5 when i eventually pull under a red light but hey, im savin the gas, they can nail it before a light if they want to. btw i have a SICK disease where i dont like to pass 2k rpm besides good reasons, and 2.71 a gallon for 93 mobil octane increases my gas mileage too, i think its well worth it. just got my speedpass now that you get 5 cents off every gallon

[bcampbell]

Originally Posted by dmasjz45

if it started using twice as much then it might be more serious of a problem such as a gas leak, have you noticed any spills on your driveway or the smell of gas when driving or after parking? any smell coming from the engine bay? it would take quite a huge combination of problems to change mileage from 20 to 10, regarding its a deffinate loss in gas mileage. i usually get 25-27 mpg on my gt, but shes in great condition all around with 86k miles, and i even abuse her sometimes too. of course thats a combination of highway/city but i do more city. im sure it attributes to all the people i piss off when i coast from 40 to 5 when i eventually pull under a red light but hey, im savin the gas, they can nail it before a light if they want to. btw i have a SICK disease where i dont like to pass 2k rpm besides good reasons, and 2.71 a gallon for 93 mobil octane increases my gas mileage too, i think its well worth it. just got my speedpass now that you get 5 cents off every gallon

a couple times just recently, i thought i could smell gas. once while i was driving, and another time while i was at the gas station but i just figured it was probably the truck in front of me or duh!...i'm at the gas station. but it was strong enough both times that i looked under my car when i got home to see if anything was leaking. i didn't see anything.
i need to check what i'm really getting on mpg, i just haven't been able to fill it up for a while. gas is so high i almost need to save up!

[bcampbell]

Originally Posted by jessep28

Mine was only getting 18-20 in mostly city driving with the A/C on during our heat spell here in NE. I don't gun the car either or drive it like I stole the thing.

However, that could be attributed to bad plugs and wires causing my random misfire problem, so I just had that fixed.

Learned during that repair that my fuel filter was original at 45 k (yikes!) and air filter was dirty. Kudos to the dealer for not doing that during the turnaround before I bought it, so I just did all that this weekend. But it was my fault for not checking.

I filled up last night and milage was 21.3...not bad but not great either. But this will be my first full tank sicne I fixed all that stuff though.

Sorry for babbling.

hey babbling is fine with me...that's where i learn everything so i say "BABBLE ON...!"
ok- fyi on the dealerships... i bought mine at 59k and i'm a girl so i don't really know all the things you should be checking for such as fuel filter and stuff like that. i finally had the transmission flushed at 85k miles because that's when they told me they don't do that stuff. they said when they buy it at auction or get it through trade in.... even if it needs it, they don't do it. but they are expecting people like me to know it needs it and then pay them to do it. which i did pay...somewhere else.