Bad Gas Mileage [Merged 9-6]

[99GST]

I am still getting some pretty bad gas mileage.

I am only getting about 19.7 mpg with mostly city driving shifting at 4k.
I have already replaced my front O2 sensor and am looking to replace the fuel filter.

I have a 99gst with about 55k miles on it. Should my fuel filter already be bad?

What else should I check or change? I have NKG plugs and Accel wires are on the way.

Thanks,
Nathan

 

[sprfunk]

Which heat range do you suggest and where is the best place to buy them? Also, I heard the bosch o2's are worthless?

Schucks is were I got them, most places have them though. If you go to Schucks call them first and you should get a %10 discount. The only thing is, they don't show up on the computers as a 2g plug, they show up for a 1g plug, so ask for the model number, not for what they think goes on the car.
I had some plat plugs on mine for a while, and it never ran well with them, and my idle has been screwy, I replaced them and it is less screwy...WTF
You do a search on this sight for seafoam, I have not used it yet (I broke my BOV trying to get my suction line off it) but I have 2 bottles ready. From all the people who wrote about it, it could be worth it, and you should do it since your going to replace your spark plugs anyway, just do it with the old ones, before you replace them.

 

[dsmotors09]

Schucks is were I got them, most places have them though. If you go to Schucks call them first and you should get a %10 discount. The only thing is, they don't show up on the computers as a 2g plug, they show up for a 1g plug, so ask for the model number, not for what they think goes on the car.
I had some plat plugs on mine for a while, and it never ran well with them, and my idle has been screwy, I replaced them and it is less screwy...WTF
You do a search on this sight for seafoam, I have not used it yet (I broke my BOV trying to get my suction line off it) but I have 2 bottles ready. From all the people who wrote about it, it could be worth it, and you should do it since your going to replace your spark plugs anyway, just do it with the old ones, before you replace them.

I don't have a Schucks store anywhere around here. Any website or place to get them? I also have seafoam in my garage as we speak.

 

[talonz27]

The numbers 6.7.8. etc. are the heat range indicators. Get the 6's.

The Bosch sensors are not a plug n play. You have to manually wire them into the harness. This is why people say they are crap. AFAIK, they work as well as an OEM sensor.

The bosch sensors i got from checker are plug n play ready to go. so it all depends on what ones you buy, the universal or the direct fit.

 

[sprfunk]

I don't have a Schucks store anywhere around here. Any website or place to get them? I also have seafoam in my garage as we speak.

What parts shop do you have? Most places will have them... This is the web site. You should do a search for spark plugs and see how many people suggest this plug. NGK Spark Plugs USA

 

[dsmotors09]

What parts shop do you have? Most places will have them... This is the web site. You should do a search for spark plugs and see how many people suggest this plug. NGK Spark Plugs USA

Toyota didn't say the brand all they said is the cheapest brand, they recommended factory plugs like I said from mitsubishi, because they said it was a high performance car.

 

[matthewdesigns]

The bosch sensors i got from checker are plug n play ready to go. so it all depends on what ones you buy, the universal or the direct fit.

Thanks for the correction

 

[sprfunk]

Toyota didn't say the brand all they said is the cheapest brand, they recommended factory plugs like I said from mitsubishi, because they said it was a high performance car.

Do a search on what plugs people use, and 99 out of 100 people use NGK BPR6ES, and comment on how good they work for our particular cars. If you go this rout any part stores should have them, I would not go to the dealer for spark plugs because these cheap ones work better then the "high performance" plugs in our car. Don't take my word for it do a search and find out.

 

[ktmrider]

Do a search on what plugs people use, and 99 out of 100 people use NGK BPR6ES, and comment on how good they work for our particular cars. If you go this rout any part stores should have them, I would not go to the dealer for spark plugs because these cheap ones work better then the "high performance" plugs in our car. Don't take my word for it do a search and find out.

+1
The number idicates the heat range, but understand that a larger number, B8, is "colder" than a B6 ( stock ). Folks with big power mods start using colder plugs to reduce detonation and prevent engine damage. Using colder plugs on a stock or near stock engine will only increase emissions and lower fuel economy ( more unburned fuel ).
Autozone carries these plugs, so does Napa.

 

[99GsxMD]

I have read all these posts and i still cant figure out what to do to fix my gas problem. I am getting around 150 miles to a tank. Anyone know whats up?


Mods: Intake, Ic Piping, greddy rs bov, autometer boost and a/f gauges.

 

[justoscar1]

boost leak somewhere maybe

 

[99GsxMD]

boost leak somewhere maybe

Thats what a lot of people are saying but how bad can that make my milage if i am not boosting that often. I have calm driving haibts and i only boost when i need too. I do have a boost leak checker on the way and a new os sensor. If that doesnt fix it, what else could i try?

Also does boost leaks kill hp?

 

[Laysher91]

What about: plugs, wires, air filter, fuel filter, fuel system cleaner, seafoam, correct tire pressure, malfunctioning MAF...etc. Try doing some maintanence to see if your situation improves.

 

[99GsxMD]

What about: plugs, wires, air filter, fuel filter, fuel system cleaner, seafoam, correct tire pressure, malfunctioning MAF...etc. Try doing some maintanence to see if your situation improves.

I have done the wires, plugs, cleaned the filter, did a fuel system clean, i do have the correct tire pressure...

 

[dsmotors09]

I replaced the spark plugs, but when it snowed I didn't drive my car (preventing rust), and I had ONE mile on the trip because I went to get gas the night before it snowed, and after a week or so when the snow melted I went to drive it and I lost a 1/4 of a tank

 

[webconnect]

After the car is primed (about 1-2 minutes of driving) of fuel, the gauge will show less. (Starting and warming up take a lot of fuel.)

Also, gas is more dense when it's cold. Thus filling up more volume.

 

[joe sobo]

my brothers gst-spyder with just a intake as a mod gets 175 miles to a tank if you think its running wrong,,,,,,, we just took it through n.j inspection and it passed with flying colors,,( and anyone from jersey knows how strict they are on emmisions and all . why could this be????????????????

 

[99GsxMD]

I have changed the spark plugs, spark plug wires, o2 sensor, and getting ready to cahnge the fuel filter... What could be the damn problem? It's getting really old only getting 200 miles to a full tank of gas. With gas at $3.20 ++++, i need to fix this. Any help would be awesome.

Also i just installed a FMIC, and it seems like everytime i shift into 3rd, 4th, 5th, my exhaust makes a loud pop, and seems to backfire. I dunno what that could be. I have a list of everything done to my car.

 

[dreamnevo]

Check for boost leaks

 

[98GSXtreme07]

You've done all of that and still bad gas mileage!? Dang...I too am tired of getting 200 miles to a tank. Well I actually get slightly more. I'm about to do my o2 sensor as well as fuel filter. Not very incouraging. Anway, enough of my ramble. Have you tried seafoam? When I did it, it actually got rid of my lifter tick but that only lasted a few weeks and it came back. My gas mileage did go up from 15 to 20 though. Also maybe taking it to a trusted shop and getting the fuel injector treatment? Not sure how much this would help but cleaning the throttle body. I remember seeing a post a few months ago of where they had done some work to their car, I can't remember what but it was just a few things, and their gas mileage went from 20 to 28. It was on a turbo awd, if memory serves me correctly. I hope this helps you in some way if only a little.

 

[PIMking]

I get 250ish a tank. But I would like to find out were gas is 3.20 a gallon.

 

[Executionerhk]

I get 250ish a tank. But I would like to find out were gas is 3.20 a gallon.

250? is that good or bad...
local driving?

i have bad mileage too...
12 mpg on local...
i need to go get my car check out...

 

[98GSXtreme07]

250ish city is like 17 or so mpg. Not too good. And what sucks about gas prices is that its starting to become the norm for it to be 3 dollars a gallon. I think we'll be lucky to ever see regular unleaded (89) go down as far as 2.50 a gallon. There I go again rambling.

 

[Boost92awd]

Have you changed the PCV valve? Check for boost leaks? Do you have a logger? A stock turbo DSM should get anywhere from 19-24 MPG. Depending on your driving. A cloged fuel filter will only be wasting fuel at idle, once driving it will cause a lean condition.

 

[gsx951]

Egads, what AFR's are you guys running?

I get 17mpg in local traffic when I'm hammering the snot out of the car and 21mpg when I drive concervatively.

 

[dsmsucks]

Not that this applies to any of you but a friend of mine was crying about his gas milage. I took a ride with him and figured part of the reason. He shifts at 3500 thru 4000 rpms . I shift at 2000 to 2500 rpms. He was like damn you car is better on gas then mines