Horrible Gas Mileage! I need help!

Blak05GT

New Member
Oct 30, 2007
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I have a pretty serious gas mileage problem. I have an '05 GT with the usual light bolt-ons. I tested my gas mileage and it's somewhere between 10-15 mpg depending on how much highway driving I do. The air filter is fine, the car has only 9000 miles on it and drives perfectly. I am a college student and can't afford to keep filling this thing up every 200 miles or less! Any help would be greatly appreciated.
 
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Wow, that's really bad. I would clean your throttle body. Maybe try changing gas stations, you may be getting some gas that has water in it. Also check your fuel filter and spark plugs. See if that helps.
 
Thanks for that advice. The gas isn't the issue as I've filled up at more than a handful of different gas stations and I always put 91 octane in it. I'll check those other things.
 
Dude, that car is too fresh to be having any problems. Only 9000 miles on an '05? I wish. I have almost 40000 on mine. I guess anything could happen though. Are you sure its not a problem with your foot? I get about 15 MPG on my '05 stick but its totally my fault. Damn size 13 Filas...
 
Also switch to all synthetic fluids in the engine, tranny and rear diff. That is bad mpg, my GT isn't even broke in yet and I get 22 mpg around home and 25 on a trip. Have you swapped on taller tires or wheels? If so, if you don't get the speedo corrected your figures won't be correct.
 
I know this is pretty basic but, the first thing I'd look for is a fuel leak being you say it smells rich. I get 25 at 65 and 23 at 80, both on the flat and on cruise control.
 
Check tire pressures, amke sure they are over 30 psi.

How far re your trips? if you are only running a couple miles at each start, the engine is running a little rich to heat up the cat.

try starting in 2nd for a tank.

Tom
 
Also, if you're driving mostly short trips like SlideWRX mentioned, and you go from light to light in city traffic in cold weather, then 10-15 mpg is about all you'll get. FWIW, my mother's Focus gets only 20 mpg around town in the winter, but she normally travels only a mile or 2 each way.
But if you're getting only 15 mpg max during long highway trips, then something is definitely amiss.
 
Exactly what you mean by light bolt on? What I'm getting at is this, before I bought my CAI and tune I tanked up with Super Plus @ 93 octane and the car ran like crap, although I didn't measure the gas mileage I'm sure it was horrible. When that was done I went back to normal unleaded @ 87 octane and the car ran fine. Perhaps your (and this is only a guess) you are running too much octane if you don't have a tune.
 
A lot of my driving is in town. It's about 4 miles to work and 4 miles back. That with a stop or two at Wal-Mart usually gives me 13.4 miles per gallon. I can't get any better no matter how hard I try.
On the road I have gotten as much as 28 miles per gallon.
 
Get a good dyno tune...

I get about 18mpg city and 28mpg (80mph) cruzn' I-10 with 4.10's on an efficient tune... A race or torque tune will yeild less mpg.

The money spent on a good tune at a reputable dyno will save you that much $$ and more in a years time in gas..:D AND get the best performance out of YOUR specific car.:nice:

Just my 2c

Best of luck with MOOOOtang and school.
 
I drive the piss out of my car and I get no lower than 17-18 mpg. Did you change rear drive gears by chance?

Come to think of it...my wife had an 06 VW Beetle Convertible that got 12 to 13 mpg and the dealer was never able to figure out why. We traded it in for a new one, of the same exact model and motor size and it got 24 mpg. We did every thing possible to the car from changing the fuel tank to the injectors. We were never able to figure it out. So, the dealer took it back. I am not a firm believer of VW, Audi or Porsche anyway. But, her dad works for Audi so we can't beat the deals.
 
Thanks for everyone's input. I'm thinking about getting a quick check-up at a shop to make sure there are no clogs anywhere in the system or something like that. I'm also considering a tuner like the SCT Xcalibator or DiabloSport Predator. Anyone think those might help? Now to answer a few people's questions.....light bolt-ons are an MMR CAI, JBA headers, and a B&B exhaust. The car is also lowered an inch and has 18's in the front with 19's in the rear. The tire pressure is fine and I don't have a heavy foot. I get on it once in a while but even on the highway when I'm cruising at 70-80 in 5th gear the gauge goes down like crazy.
 
I'm surprised that nobody else has mentioned this, but if you do not have a tune in the car to run 91 octane (which it sounds like you don't) this is your problem....

Higher octane fuel burns slower than a lower octane. A higher octane fuel such a 91 or 93 gives you the ABILITY to make more power, it doesn't make it on its own. If you're tuned correctly for it, its a great thing. If you aren't tuned, it will only hurt your performance, both power wise, and economically.

Assuming that you aren't tuned, fill up with some plain old 87 octane, and I promise your mileage will improve. I still don't understand why most of America believes that premium fuel is somehow magically "better" for your motor, no offense to you personally....:nice: