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Old 01-20-2007, 10:13 PM   #1
vipergtrdj
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Default bad gas mileage

well I just bought my subaru a week ago. now i didnt get any mantienance records or anything for the car.all i know is all the driving is highway miles and the clutch feels brand new - it pulls great and still has a lot of power.

well i realized today that it was drinking down gas like it was nothing, i look underneath to make sure its not a leak anywhere -- no leaks. it has a 13gallon tank and i can only go between 220-250miles on a tank .. so that calculates to be about 19-20mpg .... my girlfriends car is identical -- and with me driving her car gets anywhere from 23-27mpg .... they both have the 2.2l engines,
i was just wondering why mine is so low on the gas mileage.

Could it be the air filter,oil, spark plugs/wires/ or distributor cap ? would changing any of those help ?
can anyone give me some suggestions please ?

thanks in advanced.
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Old 01-20-2007, 10:43 PM   #2
Meat Supply
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yeah, those sound like good places too start, also check fuel filter. air filter
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Old 01-20-2007, 11:46 PM   #3
ivwarrior
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Well, considering a Subaru hasn't used a distributer in years, I doubt it's the distributer cap.

If you don't know any of the service history on the car, I'd start with spark plugs (NGK) and wires (OEM) and fuel and air filters, maybe PCV valve just because it's cheap and easy.
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Old 01-21-2007, 09:50 AM   #4
vipergtrdj
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alright ... thanks.... im gonna do the air filter, then wednesday do the spark plugsand wires......
i didnt know they didnt use distributors ...
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Old 01-21-2007, 11:53 AM   #5
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theres a cap looking thing, but no distributor underneath. but it's direct spark like most new cars.

my MAF had weird effects on my MPG even before it had negative effects at idle. depending on mileage, i'd check that also. swap MAF's from your GF's car to test it maybe? just a thought.

what tire sizes are on both cars? wider has more drag/friction fwiw. lighter wheels would act similar. but thats a stretch having seriously different sizes or weights of wheels between the 2 cars. but is possible, just not probable.

sticky drum brakes in back? mine would stick but make no noise on my old L sedan. noticeable usually in reverse when drum sticks from sitting, then suddenly pops free.

--keith
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Old 01-21-2007, 01:47 PM   #6
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Hold on a moment. How exactly are you calculating your mileage again?

You're dividing the number of miles between fill ups by the number of gallons you actually added, correct? Your post makes it sound like you're dividing by the total tank capacity of 13 gallons.
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Old 01-21-2007, 01:58 PM   #7
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Vipergtrdj, is your car a WRX or an NA RS?

Based on my numbers, my RS (2.5i MY06) gets about 27MPG or 8.7L/100km highway on 87 Octane (I made a post in the the NA forum with all the details if you're interested.

I'm curious as to what is your driving style and shift-points? I've found that Subaru's really do react drastically with different driving styles. I personally commute alot every day so my driving style is quite relaxed.
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Old 01-21-2007, 08:22 PM   #8
vipergtrdj
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i am dividing 13gallons (capacity of the tank when its full) and i ran it to empty this past fillup to see what my mileage was. it was at E and started to spit and sputter like it was out of gas, that was at 237miles on a full tank .... so thats about 18-19mpg .... i believe thats the correct way to calculate it ....

i usually shift about 2500 or so, i try not to go above 3k unless going up a hill then i usually just shift at 3k, but im not taking hills every day. my driving is usually relaxed, i comute a lot to work so i take it easy.
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Old 01-21-2007, 09:01 PM   #9
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No, the "correct" way to calculate is dividing the miles you put on, by the gallons of gas you "actually" put in, to fill it up again...
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Old 01-21-2007, 09:48 PM   #10
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Quote:
Originally Posted by vipergtrdj View Post
i am dividing 13gallons (capacity of the tank when its full) and i ran it to empty this past fillup to see what my mileage was. it was at E and started to spit and sputter like it was out of gas, that was at 237miles on a full tank .... so thats about 18-19mpg .... i believe thats the correct way to calculate it ....

i usually shift about 2500 or so, i try not to go above 3k unless going up a hill then i usually just shift at 3k, but im not taking hills every day. my driving is usually relaxed, i comute a lot to work so i take it easy.
Quote:
Originally Posted by wrxdrvr View Post
No, the "correct" way to calculate is dividing the miles you put on, by the gallons of gas you "actually" put in, to fill it up again...
^^^+1
And you shouldn't be running the car to a completely empty tank!!!
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Old 01-22-2007, 06:36 AM   #11
vipergtrdj
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Quote:
Originally Posted by Impresario View Post
^^^+1
And you shouldn't be running the car to a completely empty tank!!!

i only ran it to a completely empty tank this once to see what gas mileage was. didnt think of the other way of doing it lol ill try changing the plugs and see what happens. thanks.
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Old 01-22-2007, 09:14 AM   #12
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Viper, you don't have to run the tank empty to compute mileage. All you have to do is use the number of gallons actually added from one fill up to the next. That should be right there on the pump and on the receipt.
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Old 01-21-2007, 09:16 PM   #13
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i get about 20 or less on my wrx, i could probably get more if i drove more conservative
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Old 01-21-2007, 09:26 PM   #14
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thats about what i get, i never thought anything of it
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Old 01-21-2007, 09:54 PM   #15
Subie Gal
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front 02 sensor

CEL or no.... i bet that it's going or has gone bad....


Just went through this on my 2001....

Jamie
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Old 01-21-2007, 10:50 PM   #16
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i was getting 19 in my 2.0L heavily modded. changed the plugs and now i get 24.
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Old 01-22-2007, 05:11 PM   #17
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We have found spark plugs, and air filters to be the #1 cause of poor fuel mileage. Also, Fram air filters seem to cause a large loss of fuel mileage. I get well over 300 miles a tank with my modded WRX
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Old 01-26-2007, 07:24 PM   #18
vipergtrdj
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Quote:
Originally Posted by crampfan View Post
We have found spark plugs, and air filters to be the #1 cause of poor fuel mileage. Also, Fram air filters seem to cause a large loss of fuel mileage. I get well over 300 miles a tank with my modded WRX

what about the wires ? should i jsut do the plugs and then see if anything changes ?
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Old 01-26-2007, 07:44 PM   #19
Sir-Knight
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how cold is it where you drive/live? I'm experiencing an average of 20-30% more consumption at -20 degrees C vs +10 degrees C. Cold weather might account for part of your crappy fuel equation. My car is only 3 months old, so nothing mentioned could possibly be affecting mileage that badly.
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Old 01-26-2007, 07:46 PM   #20
vipergtrdj
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i live in vermont ... and yes its a bit cold lol its about -20 at night and about 0 when i go to work and when im done with work.
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Old 02-14-2007, 11:44 PM   #21
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I just recently bought an '05 WRX and was shocked to see it get as bad of gas mileage as it does. I think I got over 21 mpg once or twice on some of my longer trips but average more in the 18-20 mpg range. I have got as low as 17 recently. It is winter time so I can only hope I can pull some better mileage when it warms up some. I guess I was just hoping for more in the mid-20s. The car only had 16K on it when I bought it so I doubt its any sort of mechanical issue. Turbo+AWD = gas guzzling it seems.
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Old 02-15-2007, 09:52 AM   #22
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These cars should not be getting such bad milage, unless driven hard and with many short trips (richer AFR when engine is cold). I have been tracking my milage (over a years worth of data) 2003 wrx Cobb stage 2 and have averaged 24.32 mpg with a 1.25 standard deviation.
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