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

 

[TSI_1G_90]

I usually get 250

 

[slonkey]

Hmmmm why would I get 400+ before

 

[Anubis_4_99]

Did your driving habits change? Pass more people then normal? Get a little boost happy?

Anything from tire pressure to foot pressure can effect your milage.

 

[slonkey]

Lol if anything I was driving worse then. But I might have low psi in tires. I'll check that

 

[MikeSD]

400+ on a tank? was it being towed by a prius?
Seriously though, that would be like 33 mpg. That is far more than I have ever gotten on my mostly stock setup driving like the old man that I am.

 

[Abe'sGST]

Tire pressure can't affect mpg that bad. Are you sure you weren't getting some more like 350 miles to a full tank? That's what I'm getting on almost all stock.

 

[97gst_spyder]

I got 350-400 miles a tank when I was FWD. Once I went AWD, I'm lucky to hit 250.....

If the mileage went down after fixing the leak, you either A - are in boost alot more than you ever were before. Or B - now have a nice leak at the turbo to manifold gasket...

 

[hypergenesis]

400+ on a tank? was it being towed by a prius?
Seriously though, that would be like 33 mpg. That is far more than I have ever gotten on my mostly stock setup driving like the old man that I am.

My GST on simple bolt ons and a little commuter tune got 32mpg for the whole tank Reliably. I always broke 400 miles to the tank and that included messing around and what not.

 

[MikeSD]

My GST on simple bolt ons and a little commuter tune got 32mpg for the whole tank Reliably. I always broke 400 miles to the tank and that included messing around and what not.

that is pretty amazing, my gsx has never gotten close to that.
Right now I am getting about 270.

 

[95talongirl]

FWD will see better fuel economy than AWD. With the extra weight and drive wheels, you loose economy. This is why some manufacturers go with an "on demand" AWD system. Basically its 2WD until it needs AWD.

Kinda off topic, but it is true that our FWD cousins will get better gas mileage.

 

[slonkey]

Tire pressure can't affect mpg that bad. Are you sure you weren't getting some more like 350 miles to a full tank? That's what I'm getting on almost all stock.

Nope was 400+ now I just refilled and it was below E. that was reading 237miles

FWD will see better fuel economy than AWD. With the extra weight and drive wheels, you loose economy. This is why some manufacturers go with an "on demand" AWD system. Basically its 2WD until it needs AWD.

Kinda off topic, but it is true that our FWD cousins will get better gas mileage.

I have fwd. Gst 97. Still crap gas mileage

I got 350-400 miles a tank when I was FWD. Once I went AWD, I'm lucky to hit 250.....

If the mileage went down after fixing the leak, you either A - are in boost alot more than you ever were before. Or B - now have a nice leak at the turbo to manifold gasket...

I am fwd, always have been. It went down a lot.

 

[007jimmy]

Before i had link i would disconnect my battery to clear my fuel trims after i fixed boost leaks and such.. I was told it could help on a stock ecu. I figured what the hell and did it anyways. It didnt hurt anything the couple times i did it but i also payed no mind to my mileage to see if there was an increase.

 

[my dreamt dsm]

Wow, you guys get a lot. I only get about 230ish a full tank... I use to get more.

Thread will be merge in 5...4...3...2...1.

edit:

I use to get more mpg. Now it's really crappy. I read through most of this and lots of peeps are saying it's a o2 sensor thing. Even though it's throwing no codes. It can't be bad????? Can it?

 

[slonkey]

Wow, you guys get a lot. I only get about 230ish a full tank... I use to get more.

Thread will be merge in 5...4...3...2...1.

edit:

I use to get more mpg. Now it's really crappy. I read through most of this and lots of peeps are saying it's a o2 sensor thing. Even though it's throwing no codes. It can't be bad????? Can it?

I'm in the same boat. Lol I used to be pro on full tank. Now I am at the gas station all week

 

[xGrafitti]

Ok, I had a different post but decided to make a new one. I've had problems with my gas mileage, and I took my car to AutoZone and had them do a diagnostic on my car.. This is what it says...

Explanation:
The powertrain control module uses the oxygen sensor to calculate the Air/Fuel ratio of the engine. The computer has recognized a rich or lean condition on the engine bank only.

Probable cause:
-If bank one and two codes set together suspect fuel pressure or MAF sensor
-Oxygen sensor defective
-Ignition misfire-repair
-Fuel Injector Problem



My self I'm thinking it's a defective Oxygen Sensor, but I want a few other opinions. Also how can I find out which Oxygen Sensor it is?

 

[assassin3117]

If bank 1 and 2? our cars dont have two banks. You have bank 1 sensor 1 and bank 1 sensor 2 with sensor 2 being the one that monitors your cat. If you had a injector issue or a ignition misfire you would feel it, especially if your gas mileage is that bad. Use a data logger and watch your fuel trims.

 

[xGrafitti]

If bank 1 and 2? our cars dont have two banks. You have bank 1 sensor 1 and bank 1 sensor 2 with sensor 2 being the one that monitors your cat. If you had a injector issue or a ignition misfire you would feel it, especially if your gas mileage is that bad. Use a data logger and watch your fuel trims.

Ok, so you're thinking it's definitely one of my sensors right? And I don't have a data logger sadly.

 

[Calan]

Ok, I had a different post but decided to make a new one.

Why?

 

[assassin3117]

It could be your up stream sensor. but you should get some type of data logger. Its a great tool to keep in your car. Your MpG could be a few things. Is your Cel on? are you feeling any type of misfire?

 

[xGrafitti]

Why?

Deleted the old one.

It could be your up stream sensor. but you should get some type of data logger. Its a great tool to keep in your car. Your MpG could be a few things. Is your Cel on? are you feeling any type of misfire?

Sorry, you may call me a noob, But what i a Cel? And No I don't feel and type of misfire or sputtering. Where can I get my hands on a data logger?

Ok after a little research I see that my error code P0170 people are saying that i should change my front o2?

 

[MikeSD]

CEL = check engine light

 

[Fast-Orange]

The front o2 sensor on these cars are notorious for becoming very lazy and not failing completely. In turn they often DO NOT throw a CEL on. The rear o2 sensors only purpose is to monitor your catalyst efficiency, it does not affect fuel trim. As far as milage i usually get around 400-430kilometers per tank so about 10L/100km average in my 97 awd.

 

[xGrafitti]

CEL = check engine light

Ok, yes my cel light is on.

 

[bowens1414]

hello all i recently bought a 4g63 but one small problem. my gas mileage is horrible. now im trying to confirm but also trying to find out approximately how many mpg im getting. i dont have a dsm link so i cant do it the easy way. but anyways i thinks its my cars running rich due to me only running wastegate boost on the t-25 about 5 lbs (bought it like this) can anyone confirm.??

much thanks

 

[Kalub]

First, that is not stock boost pressure on a T25. I would suspect that you have a major boost leak. Build a boost leak tester. Also are you pulling any DTC's? A bad front O2 sensor can cause the car to not enter closed loop, and your MPG as well as low throttle cruising will suffer.

However, I still think you have a bad boost leak, and you are leaking metered air to atmosphere. (Meaning your ECU is injecting fuel, however the air is not there causing you to run extremely rich)

Good luck!