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

 

[gstspyder1998]

I get about 22 mpg on my car and I just hit 60k miles. That's about 320 miles per tank or 14.1 gallons. I usually get more on long trips.

 

[purplefever]

320 miles to the tank? damnit i only get 275-290 on my gst. that sux

 

[gstspyder1998]

Originally posted by purplefever
320 miles to the tank? damnit i only get 275-290 on my gst. that sux

Probably because your car is hella modded.

 

[Slanted J]

I get around 17 mpg. Mostly city driving

 

[Blk95gs]

quit complaining......as of yesterday, my pos decides "hey, lets use an eighth tank of gas to go 15 miles" so yea thats about 100 miles per tank...

 

[gstspyder1998]

Originally posted by Blk95gs
quit complaining......as of yesterday, my pos decides "hey, lets use an eighth tank of gas to go 15 miles" so yea thats about 100 miles per tank...

Damn, what's wrong with your car???

 

[Dannyboy1201]

Holly thats a bunch of fuel your burning.. HuMm that doesnt sound right..

 

[4u2nv]

Man, I have had that same problem for a while...I also get about 220-240 miles on the tank, and that's normal driving.....
Difference is that I'm venting to the atmosphere...yeah yeah...I know it's bad.....But my car just runs like sh!t when venting back in...It all started when I put my Type S BOV....I don't know what to do...

I'm out...

4u2nv

 

[CyberDSM]

What kind of mileage are you guys getting? I'm only getting about 160 miles per full tank. Considering the 15.8 gallon fuel capacity, im only getting about 10 miles per gallon compared to the stock 20 miles per gallon. I've read that it might be a faulty o2 sensor or thermostat. My question is, has anyone had this problem and if so how much was it to replace the o2 sensor or thermostat. Does anyone have any other ideas why I might be getting such crappy mileage. I thought it was just because I was pushing the car a lot.

 

[Dannyboy1201]

Im actually going thru this problem as we speak i found a o2 sensor for my car it only cost me 66 bucks thats about as cheap as they come here is the siteConicelli

 

[CyberDSM]

Did your car throw a check engine light? Mine hasn't? I heard that you have to be driving over 45 mph for at least 30 min for it to notice you have a bad 02 sensor, and I just recently drove 1hour and a half at 80mph and I still didn't get check engine light. Thanks for the link, but I don't want to spend 60 bucks on an o2 sensor to find out thats not the problem. I've also heard it could be my thermostat. Does anyone know how I can check to see if my thermostat is bad?

 

[L2RTSiAWD]

My O2 is bad and it tripped the CEL on my car.

Before bad O2=230 to a tank(all city driving)
After bad O2=150 to a tank ( all city driving)

Later,

 

[eclipze23109]

im only getting about 160 miles on a full tank of gas on my 98 gst anyone know what i can do to improve the mileage? thanks.

 

[kylemoto]

Starts with driving habits. Go easy on the gas (I know, hard to do with the turbo power), cruise at something closer to the speed limits, etc. This is probably the largest single thing you can do to get better mileage.

As far as the car goes:
- O2 sensor, check and replace if needed.
- timing, check.
-Throttle position sensor readings, check and adjust if needed.
- temperature sensor working?
- crankshaft position sensor
- fuel pump relief, check
- egr valve, check
- air leaks in the intake tract


these are just some of the things to look into. Good luck

Kyle

 

[Nexius]

Something is wrong with your car because I also have a 98 GS-T and I can get 240 miles on one tank of gas. Unless you're driving at WOT all the time !
Does the car still pull as much ? Are there any problems with the car except the gas mileage ? Is the check engine light on ?

 

[eclipze23109]

no, i drive it normal most of the time...and no the check engine light is not on, and as far as i know, nothing else is wrong with the car

 

[Nexius]

Did you ever change you gas filter ? start with that if you never changed it. Do you vent your BOV back into your intake ? because if you vent to the atmosphere in stop and go situatiuons you will have very bad gas mileage. If you have a boost controller try to turn it way down and see if that makes a difference.. it did for me when I had the original turbo in the car. Check for boost leaks, disconnected hoses...ect... it could be just about anything, do the obvious and work your way down from there.

Goog luck.
Nexius.

 

[tokyo_tad]

I've been getting bad gas mileage for a while now. I actually hit an all time low of 13 MPG so I replaced the O2 sensor which I thought to be bad. Now even with 50-50 highway/city I still only get 18 MPG. WTF is going on? I look at my A/F gauge and the sucker is fluctuating at idle like it should but I did notice that its going to RICH when I'm halfway on the gas? Do I need to get my injectors recalibrated or what? I haven't replaced my fuel filter in a while but I would think that would cause a lean condition. Not a rich one. Anyhow, this is boggling me. Oh and I drive an auto. I'm really tempted to just dump this Auto DSM for a 5sp DSM at a local dealer.

 

[CBgst]

what are your mods

 

[fivestardsm]

How long's it been since you changed your plugs and wires

 

[tokyo_tad]

its been 10k or so since I got plugs but didn't replace the wires cause they looked fine. I guess I should buy new wires but if its not arc'ing then no need right?

Mods are simple stuff 1G BOV, UIP, intake, and that's about it.

 

[fivestardsm]

Not nessicarally(sp?)... I changed my plugs and wires and got a lot better mileage. They weren't really that bad, but hey for $40-$50 bucks, what the hell, It pays off in the long run.

Also I run hard, so i try to replace my plugs every 5 or 6 thousand miles....Or less!!

How much are the wires on a 2g, i haven't had my 95 long enough to replace them ... It might be more.

And how do you spell that word, nesci...nessic....Oh s@#t, I don't know

 

[97GSTURBO]

I have a 97 auto GST and was having the same prob, first thing was that the hose on the FPR was loose and popped while I was driving down the road. (Zip tie fixed that) Still not so good gas mileage. Changed to NGK plugs and wires, better but not so good still. Redline Fuel system cleaner in a tank with 2 gallons of 110 and the rest 91 about 3 months ago, and it's been getting about 20-25 to the gallon now and I'm spooling a lot!

 

[venom2097]

Check your air filter, mine was turning black. Gained 5mpg after changeing