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Old 08-19-2010, 01:33 AM   #1
kewlboxer2
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Default Sick of ****ty fuel mileage

Once upon a time my 2.5i was able to get 30 city and 35+ highway. Now its a dismal 22-23 city and 27 highway. Car currently has 96k on it.

Thought it was my ****ty used RS cat that I bought for my borla headers, so I hollowed them out Sunday. Still no change in mileage. Im running 93 octane and tune from Phattbotti, hybrid 3 inch intake.

Plugs/wires good. Only have about 10k on them.

Could it be the un-replaceable fuel filter?
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Old 08-19-2010, 02:50 AM   #2
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Quote:
Originally Posted by kewlboxer2 View Post
Once upon a time my 2.5i was able to get 30 city and 35+ highway. Now its a dismal 22-23 city and 27 highway. Car currently has 96k on it.

Thought it was my ****ty used RS cat that I bought for my borla headers, so I hollowed them out Sunday. Still no change in mileage. Im running 93 octane and tune from Phattbotti, hybrid 3 inch intake.

Plugs/wires good. Only have about 10k on them.

Could it be the un-replaceable fuel filter?
Flash back to your stock tune and then see what your mileage is.
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Old 08-19-2010, 02:57 AM   #3
ILSMKU2
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Quote:
Originally Posted by kewlboxer2 View Post
Once upon a time my 2.5i was able to get 30 city and 35+ highway. Now its a dismal 22-23 city and 27 highway. Car currently has 96k on it.

Thought it was my ****ty used RS cat that I bought for my borla headers, so I hollowed them out Sunday. Still no change in mileage. Im running 93 octane and tune from Phattbotti, hybrid 3 inch intake.

Plugs/wires good. Only have about 10k on them.

Could it be the un-replaceable fuel filter?
You Sissy man! I get 15.9 MPG city in my STOCK 09 STI and your sniffling about 22-23 and 27 highway with 96K!
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Old 08-19-2010, 03:26 AM   #4
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you try cleaning your fuel system? injectors? etc?
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Old 08-19-2010, 03:32 AM   #5
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Quote:
Originally Posted by ILSMKU2 View Post
You Sissy man! I get 15.9 MPG city in my STOCK 09 STI and your sniffling about 22-23 and 27 highway with 96K!

15.9!? Stock!? I would be crying with that. I don't even get that driving up the mountain with 4 people, my hundred pound pup, and camping gear in a roof cargo carrier. I have a hitch installed too, I think its about 30lbs.

Premium gas and poor fuel econ was a big deal breaker for me...and i still feel like im missing out . Cant have everything tho...so I opted for saving 7k, using lesser and cheaper fuel, and having lower insurance rates.

Anyways OP. That is the nature of some cars out there...some people luck out and maintain their fuel economy but an engine wears down, becomes less efficient and there is nothing too practical that can be done to rectify it. Could definitely be your tune tho, but don't expect to get what you used to. 27 highway is still good for an AWD car.
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Old 08-19-2010, 08:02 AM   #6
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Quote:
Originally Posted by ILSMKU2 View Post
You Sissy man! I get 15.9 MPG city in my STOCK 09 STI and your sniffling about 22-23 and 27 highway with 96K!
You Sissy man! I get 12.7 MPG mixed in my NOWHERE NEAR STOCK SVX and you're sniffling about 15.9 MPG city!

I know you're not sniffling... I just wanted my share of the gas chugging limelight, too.

Yeh, if you've changed hardware and software on the car, it's no surprise. The price we pay for more powars!!!
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Old 08-19-2010, 10:58 AM   #7
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Do you have wider tires?
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Old 08-19-2010, 10:59 AM   #8
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Ill run some seafoam through the tank. I just seafoam'd the engine not too long ago. I ran a bit of lucas injector cleaner through maybe 20k ago. Its just killing me that 1/3 of my mileage is gone. I used to get 300+ at 10 gallons(3/4 tank), now its 220 at 10 gallons.

I have stock sized Bridgestone Turanza Serenity tires.
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Old 08-19-2010, 11:18 AM   #9
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From day one before any mods my 2.5i wagon always go very crappy gas mileage, probably in mid teens in city, and low 20's on the highway.

Since my uel catless setup, that has improved a little but it's still sad.

I also have a slightly heavy foot, so that could also be why.
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Old 08-19-2010, 11:58 AM   #10
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Quote:
Originally Posted by kewlboxer2 View Post
Ill run some seafoam through the tank. I just seafoam'd the engine not too long ago. I ran a bit of lucas injector cleaner through maybe 20k ago. Its just killing me that 1/3 of my mileage is gone. I used to get 300+ at 10 gallons(3/4 tank), now its 220 at 10 gallons.

I have stock sized Bridgestone Turanza Serenity tires.
This 'could' be your problem. You're not measuring your mileage accurately enough. Don't go by 300 miles on 3/4 tank and stuff. Fill your tank completely and set your trip meter at zero. Drive for at least 100 miles (to get an accurate reading)... then fill up and check how much fuel you put in via the pump. Use the same pump as you filled up before. Using a different one that shuts off at a different time may change your results +/- 2 MPG sometimes. Then report back to us.

It does sound like you have a legitimate decrease in gas mileage though. I find it very hard for you to be getting 30 MPG city and 35+ on the highway. If you estimated those numbers and did not semi-accurately test them using the method above, they're irrelevant.

With all this said, 22-23 city and 27 highway are actually accurate numbers with a manual transmission. My 4EAT sucks up gas mileage... I get 20 city and 24-25 highway... haha. AWD FTL in this respect!

Definitely willing to help... just get us some accurate numbers. I live for this gas mileage stuff having an accounting degree. I track my mileage EVERY fillup.
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Old 08-19-2010, 12:05 PM   #11
LetItSnow
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Fuelly.com is a neat way to track it. Sure, you could make up a deluxe spreadsheet and such, but you still wouldn't have this:

^^This is the answer to whether running rich to cool your charge mixed with autocross chugs fuel.

You really have to do a few sequential fills to get a fair reading.
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Old 08-19-2010, 12:56 PM   #12
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I track my mileage fairly close. I usually have to fill up every other day. I use my car for my job which has me traveling 100+ miles a day sometimes going to customers locations. I know for 100% certain I had gotten 35mpg on highway way back when my car was newish. I filled up right before I hopped on the highway, drove a tad over 100 miles and then filled up before I got home and put in a smidge less then 3 gallons. My mileage for work is consistent. I try to fill up at the same station, only 2 or 3 offer 93 octane in my area.
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Old 08-19-2010, 01:51 PM   #13
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Reading on one fill of less than 3 gallons is even worse than reading on one fill of most of the tank. I bet if you did the same before and after that fill, at least one would be dismal to make up for it.

Statistics! Quality control! Sample size!
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Old 08-20-2010, 02:44 PM   #14
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Filled up today with 93. 10.393 gallons at 240.1 miles that's 23.1 mpg. Just checked the EPA estimates for mileage and its 23 city and 28 highway.

Ill keep tracking it with fuelly.com. Its a nice little site to use.
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Old 08-20-2010, 02:52 PM   #15
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Try engine braking and coasting in neutral every chance you can get. I've noticed a 2 mpg increase by just engine braking instead of stomping on the brakes and putting it in neutral on downhill sections of the highway.
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Old 08-20-2010, 02:55 PM   #16
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I just browsed through and didn't see, did you get that mileage when you had the tune? You think with a tune you would get just as good mileage? Highly doubt it if the tune is for performance. Any modification to the intake and exhaust system will also have an effect on your gas mileage. Remove all mods and tune, then check.
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Old 08-20-2010, 03:35 PM   #17
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Mileage went down well before tune. It went down well before the headers and full exhaust as well. I noticed it about 2 years ago. In winter time(i know ****ty winter gas), i was getting 17 mpg. it picked back up to 25-27 ish when the better gas came in. at that point in time i had a SRI. So it probably has to do with my mods. It just sucks remembering 300+ miles on 10 gallons now only getting 230 to 10 gallons.
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Old 08-20-2010, 03:50 PM   #18
chazly413
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OK, I see how you get 35 mpg highway. You only did highway for that 100 miles then checked your MPG. I always go by tanks so I'm usually checking my MPG at 11-12 gallons. The best I've ever gotten was 29.8 on a 12-gallon fill-up. I think the worst was 23 or 24 in winter with ****ty transmission fluid.

@nairbmik: Do you coast in neutral down hills where just engine braking would cause you to lose speed?
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Old 08-20-2010, 05:05 PM   #19
kewlboxer2
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I usually engine break down hills. If engine breaking slows it down too much i toss it into neutral.
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Old 08-20-2010, 05:08 PM   #20
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Another means to help track your fuel mileage
www.mympgtracker.com
It's still under development, but the core bits are in place!
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Old 08-20-2010, 05:31 PM   #21
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Quote:
Originally Posted by kewlboxer2 View Post
I usually engine break down hills. If engine breaking slows it down too much i toss it into neutral.
I wouldn't really recommend popping it into neutral; who knows when you need to accelerate.
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Old 08-20-2010, 05:59 PM   #22
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Quote:
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I wouldn't really recommend popping it into neutral; who knows when you need to accelerate.
and idling requires gas, "engine braking" only requires air.
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Old 08-20-2010, 06:42 PM   #23
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Have your local gas stations switched to 10% ethanol or similar? I know here in Oregon, they made everybody switch to 10% and people started bitching like crazy about the drop in MPGs...just a thought.
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Old 08-20-2010, 07:18 PM   #24
kewlboxer2
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Yeah all the pumps say "Contains up to 10% ethanol" Im thinking 91 and 93 dont have as much in.
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Old 08-27-2010, 06:33 PM   #25
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Usually even premium gas will still have the 10% Ethanol.

If 10% ethanol not required in your area, you may be able to find premium w/out ethanol in it, but it will cost more, so it may not be worth searching out.

10% ethanol FTL! I miss plain ol' non-ethanol gas - the 10% ethanol thing "to save the environment" or "to reduce our dependence on foreign oil" is such a load of BS. My wife and I both get 10-20% worse gas mileage here in Oregon than we did in Minnesota, and it happened immediately upon arriving here, so we know it's not the extra mileage on the cars now.

For the record, I used to average around 27 mpg and now I average around 22. Some of that may be the hills here in Oregon, too.
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