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

 

[alexg1323]

i can still go a 100 miles in about a 1/4 tank on the highway. gap and check plugs, test for boost leaks definatly, makes sure your 02 still cycles normally, make sure you dont have any CELs and make sure the CEL comes on when you first start the car incase its burned out. maintance maitanence. The beuty of these cars is all the power under boost with the efficency of a 4cyl in vac. cya

 

[IamCool]

put a catalytic convertor on.

 

[Fred9981]

its auto and how do i check for vac and boost leaks

if i put the cat back on will that help


im at the point where i rather get better gas mileage and horse power ...f*cken gas prices

 

[alexg1323]

no cat isnt gonna give you 15mpg nor will removing any of the emmisions ive got running proof

 

[I-luv-em-all]

u are using premium right??

 

[Fred9981]

yes thats all i use

 

[eclipse90gsxt]

its auto and how do i check for vac and boost leaks

if i put the cat back on will that help


im at the point where i rather get better gas mileage and horse power ...f*cken gas prices

http://vfaq.com/mods/ICtester.html

Intsead of a valve steam I would drill a hole, find the correct threads and put in a end for a compressed air hose end.

 

[Tongboy]

make sure your thermostat is functioning, if the car doesn't come up to temp it'll run in warmup regulation most of the time and that kills the gas mileage

not that i know or anything

 

[GORBS88]

Sell it and buy a honda.. ...Sorry to say but if you want the power then dont complain.....I only get 18mpg at the most.. ..But if i wanted better then i would buy and honda and get 60mpg and have no power!!! If you make the HP you need to use the fuel........

 

[Dan2]

Car: 92 Talon TSI AWD, 126k miles
Mods: Big16G, 3" turboback w/ test pipe, stock IC, 550s, AFC, MAF-T/LT1 MAF, UIC, K&N, ACT2600, 255 LPH (currently not installed).

Usually the car goes 16-18 MPG depending on how I drive it and has for four years. Then today I noticed the gas was damn low considering I had only driven 130 miles. I filled it up and realized I only got 13.4 MPG. No CEL is on, and I haven't changed my driving habits. The car drives like it always has, at anything from idle to WOT.

Halfway through the tank I replaced the alternator, battery, and battery terminals/cables. The grounds are all secure and clean. I'm going to try a friend's O2 for this tank. Any other suggestions?

 

[Forced4]

My bet is on the O2. A lazy one will hurt gas mileage but may not toss the light on.

Rich
Forced 4
Good luck

 

[vaboys2ndgen]

yeah i bought mine last week and have filled up at least 5 times since then.. with 93 octane. and have only been getting 120-175miles at most to a tank.. depending on driving of course, but 175 was the most ... this is crazy, i didnt know turbo drank up that much gasoline.. any tips????????????????? :thumbdown

 

[butters]

I thought my Milage was Sh*%y untill I stopped watching the gauge and realized I had more gas then I thought. At half a tank the tank being 16 gallons It showed almost on E.

Now I just track the millage and see how much gas goes into the car at fill up.

 

[Dan2]

butters: Not sure if your reply is directed toward me, but I do track the mileage -- how else would I know the MPG?

Thanks for the reply Forced4. I'll see if I can borrow a friend's or something to test.

 

[steve]

I'll see if I can borrow a friend's or something to test.

When did you last replace the O2 sensor? If you don't know then your overdue.

Steve

 

[Bostedquest]

Also a small amount can be low tire PSI... Trust me it CAN make a difference in MPG
O2...
A far idea...
vacuum leak or semi clogged fuel filter

Is your A/F stable? any higher/lower vary alot lately? (any number of things from O2 to MAS)
How old are the brakes (possible slight drag)
Fuel pressure stable? (fuel dump valve- bypassing to lower fuel pressure)
Stable PSI (wastegate-creep can effect MPG)
Egr operating propperly?
alot of things can effect MPG that people do not regularly think of...

 

[xcelr8n]

curious, dont mean to hijack the thread but how much mpg on avg is lost from removing the egr valve. mine is now gone, and I only get about 220miles to a tank.
thanks

 

[Bostedquest]

curious, dont mean to hijack the thread but how much mpg on avg is lost from removing the egr valve. mine is now gone, and I only get about 220miles to a tank.
thanks

Really there is no telling...
I have experienced both no change, and a slight (2-3) MPG drop. Different cars, same generation of make.

Mainly it can help stabilize the combustion temp (actually lower them a little) and help reintroduce unburned gas into the engine again.

 

[xcelr8n]

what about the evap line from the tank to the canister? if you remove youre emissions lines, and that isnt plugged will that hurt mileage, I didnt bother to plug mine, and smell no gas at all, so i'm just curious..
sorry for the questions

 

[96TSi_Chris]

Its almost def. one of the o2s. Thing is, they wont throw a CEL until they are almost dead or dead completely. Throw a scanner on and pull the o2 voltage. My front oxy was pulling .37 volts and still wasnt throwing a CEL. Replaced it and jumped up 6 mpg.

 

[Bostedquest]

what about the evap line from the tank to the canister? if you remove youre emissions lines, and that isnt plugged will that hurt mileage, I didnt bother to plug mine, and smell no gas at all, so i'm just curious..
sorry for the questions

Usually evap lines on newer cars have a one way check valve to prevent that. Otherwise when the fuel pump kicks on and pressurizes the tank... the vapors reverse into the canister.

 

[jetdriven]

hell guys I get 29.5 MPG on the highway and thats boosting it up to 15 PSI about twice an hour. Oddly enough, its exactly the same as my 230K mile 91 NT talon. Exactly the same.

 

[Defiant]

Well, I commute at ...ah.... well, too fast. I get about 20. One of these times I'm going to drop down and stay out of the pedal and see how much better I can do.

But mama, that's where the fun is.....

Don't expect to get much information from the AWD fuel gauge on a 2G, because you're averaging two senders. I don't think you ever really know how much gas is in a GSX.

 

[sweet97]

Make sure that your EGR valve is working, all hoses hooked up to it. It working can make a 4 MPG difference on average. If you can afford some down time and afford it have the injectors professionally cleaned by a place like RC Engineering, if not run inj. cleaner through a couple more times than the can says.Mark

 

[DSMeclipse4G63]

Sell it and buy a honda.. ...Sorry to say but if you want the power then dont complain.....I only get 18mpg at the most.. ..But if i wanted better then i would buy and honda and get 60mpg and have no power!!! If you make the HP you need to use the fuel........

thats not true....my modded gst was , acoording to dsmtuners tuning guide, had everything for the 300hp goal and then some. I wasnt easy on the throttle AT ALL and I got over 400 miles to a tank from full to solid gas light.

all you people saying turn down the boost, and one said lean the car out?!?! thats the great thing about turbos guys, you drive around town in vacuum and get better gas mileage then a honda, and then when you want to have fun then hit the gas and have v8 power. How the f*** will a dsm do better then a honda??? well folks we have torque they dont meaning we require less throttle to put around town...that and we have turbo motor compression meaning less fuel needed to combust. how can I compare...I had a honda for 2 years stock and modded.

Oh and I switched to a a/t awd from a gst 5 speed. I get from 13mpg to 20 if I take a road trip on the highway. I have gotten less then 10 on my first full tank. its just the nature of the game folks, a/ts get less to a gallon the 5 speeds, a/t's are also heavier making more weight to push around and more gas to burn.

Andrew