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Old 10-08-2012, 10:48 PM   #1
Pickler
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Thumbs down poor highway mpg

In the city i have no problems averaging 24-26mpg depending on traffic. but on the highway doing 70mph @2800rpm i average only ~26mpg. i wonder if this has anything to do with the engine RPM being a bit high on the 4EAT? any other NA drivers have this issue?

ps. sometimes after 15-20min of highway driving my mileage starts to improve dramatically, sometimes it doesn't.
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Old 10-08-2012, 10:56 PM   #2
KevinKe
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Are you driving in "Auto" or sport shift?

I find that in auto, the rpm sits around 2.4/2.5k at 70mph, while in sport shift it's about 5k higher.

On a trip to Maine (about 4hours) I averaged 39 and was all highway - didn't use sport mode.

Part of me thinks there's some kind of overdrive that the auto mode activates to save gas or something.
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Old 10-08-2012, 11:04 PM   #3
Pickler
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i never use the sport shift unless im in twisty roads and I need engine braking. so always in D. wow 39mpg is higher than what my corolla used to get.
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Old 10-09-2012, 02:58 AM   #4
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is that ~26mpg all highway or is it more of a city/highway mix? im assuming ur getting ur milage number from the trip avg. readout next to the clock in ur car. do u reset ur trip when u fill up?
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Old 10-09-2012, 06:40 AM   #5
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Just to throw a spanner in the works, in August I did a 1300km road trip with 2.5 people (the .5 is my 3-year old), the car was fully loaded, plus 2 bikes on the back, with highway speeds around 75mph with some massive hills along the coast and got a return of 28.92mpg.
This is with a modded engine, wider stickier tyres, heavier wheels and a larger (i.e. more drag) hatch spoiler.
And I always use Sports Shift, go figure.....
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Old 10-09-2012, 12:23 PM   #6
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forgot to mention its the sedan with wrx side skirts and front/rear spoiler and 40k miles. 26mpg instant mileage from the clock while im cruising. it never goes higher unless i coast of course. i did do a highway trip with only 26mpg confirmed with my scangauge and at the fuel pump. sometimes i do better in city than highway. just seems like my car doesnt like speeds above 55mph. i had a recent tune up, spark plugs were replaced with oem parts (directly from thr box, no gapping) new fluids all around. i was told my car had an ecu flash/tune from previous owner but my mehanic reset my ecu with no result except poor throttle response now.car now takes almost 2 seconds to downshift when i floor it on thr highway.
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Old 10-09-2012, 01:25 PM   #7
Patrick Olsen
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It is unusual that your city mileage would nearly match your highway mileage. However, the 2009 2.5i is rated at 20mpg city / 27mpg highway (in the US - not sure if the Canadian ratings are the same), so 26mpg doesn't seem all that unusual to me.

The fact that the car isn't performing properly could also be contributing to the poor mileage.
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Old 10-09-2012, 03:31 PM   #8
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well yes the reason being in city i travel less than 55mph and in stop and go traffic i try to drive without brakes. but go past 55mph (2500rpm) and MPGs take a nose dive. the car is fine i have heard the 4eat is a bit slow to downshift. canadian ratings were 30mpg highway and 23 city i believe.
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Old 10-09-2012, 10:08 PM   #9
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If your reading it from the clock, that is your Average MPG. So even if you are getting 26 Avg MPG, you may be actualyl getting 27-29mpg.


What is the ratio of city:highway for you?
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Old 10-09-2012, 10:29 PM   #10
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i check mileage by resting odometer (trip A or B) then i do some travelling and review numbers. finally i verify results at the pump. for 100% highway last i checked was 26.2mpg at 70mph cruising. for 100% city last i checked was 25mpg flat. i have verified results when filing up at gas station. both the trip computer and scangauge are very accurate +/-2%.

today i decided to take the highway and logged the following
- at ~50mph (2200rpm) 36.5mpg
- at ~55mph (below 2500rpm) 33.5mpg
- at ~65mph 26.5mpg
- at ~70mph 26mpg
- at ~80mph (or 3000rpm) car averaged ~25mpg

Last edited by Pickler; 10-09-2012 at 10:42 PM.
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Old 10-09-2012, 10:31 PM   #11
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Quote:
Originally Posted by Pickler
ok i don't think i have explained this right. i reset my odometer and my scangauge then i do a highway travel and i check average. for 100% highway last i checked was 26.2mpg at 70mph cruising. for 100% city last i checked was 25mpg flat. i have verified results when filing up at gas station. both the trip computer and scangauge are very accurate +/-2%
Interesting. Are you highways flat or on an incline?
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Old 10-09-2012, 10:46 PM   #12
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Quote:
Originally Posted by theoutbackdream View Post
Interesting. Are you highways flat or on an incline?
mostly flat (toronto). some downhill when i logged this, but the return trip makes up for that error (going back uphill). even if it had to do with terrain why the sudden jump in consumption above 55mph?
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Old 10-10-2012, 12:46 PM   #13
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Quote:
Originally Posted by KevinKe View Post
Are you driving in "Auto" or sport shift?

On a trip to Maine (about 4hours) I averaged 39 and was all highway - didn't use sport mode.
.
No way Unless you were on a downhill spiral with 50mph tailwind for four hours...
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Old 10-10-2012, 01:02 PM   #14
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I've gotten nearly that high while drafting guys pulling snowmobile trailers.
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Old 10-10-2012, 01:38 PM   #15
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Quote:
Originally Posted by Pickler View Post
forgot to mention its the sedan with wrx side skirts and front/rear spoiler and 40k miles. 26mpg instant mileage from the clock while im cruising. it never goes higher unless i coast of course. i did do a highway trip with only 26mpg confirmed with my scangauge and at the fuel pump. sometimes i do better in city than highway. just seems like my car doesnt like speeds above 55mph. i had a recent tune up, spark plugs were replaced with oem parts (directly from thr box, no gapping) new fluids all around. i was told my car had an ecu flash/tune from previous owner but my mehanic reset my ecu with no result except poor throttle response now.car now takes almost 2 seconds to downshift when i floor it on thr highway.

Hey try this one day when you have time it may help the performance.

1. Record your radio setting

2. Turn off radio, a/c blower, and unplug any thing that uses power.

3. Disconnect battery both terminals

4. Cover the top of the battery terminals to make sure there is no contact

5. Touch the + and the - together (metal to metal) 10sec or more

6. Reconnect the battery

7. Start the car. Do Not Touch Anything. It will stumble and may even stall but just restart. Let it run like this for 15 mins. Then turn on the A/C and let it run for 5 min. For the next 25 drive cycles the car is going to take a sample of your driving style and record it. So don't drive like Grandma. Drive like you normally would on a daily.

What some times happens is that someone disconnects the Battery or Reflash the ECU and does not do step #7. What this does is discharges all the solenoids is the car and returns them to base, clears the what I call "How you drive" memory. OH and reset your "MPG" every time you drive for the next 100miles.
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Old 10-10-2012, 02:01 PM   #16
Counterfit
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It's relearning the long term fuel trim.
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Old 10-10-2012, 02:49 PM   #17
KevinKe
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Quote:
Originally Posted by Bluefoton View Post
No way Unless you were on a downhill spiral with 50mph tailwind for four hours...
I didn't believe it either, but it was pretty much all highway with very conservative driving. Not really any traffic either.
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Old 10-10-2012, 03:18 PM   #18
chazly413
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Quote:
Originally Posted by Wraith646 View Post
Hey try this one day when you have time it may help the performance.

1. Record your radio setting

2. Turn off radio, a/c blower, and unplug any thing that uses power.

3. Disconnect battery both terminals

4. Cover the top of the battery terminals to make sure there is no contact

5. Touch the + and the - together (metal to metal) 10sec or more

6. Reconnect the battery

7. Start the car. Do Not Touch Anything. It will stumble and may even stall but just restart. Let it run like this for 15 mins. Then turn on the A/C and let it run for 5 min. For the next 25 drive cycles the car is going to take a sample of your driving style and record it. So don't drive like Grandma. Drive like you normally would on a daily.

What some times happens is that someone disconnects the Battery or Reflash the ECU and does not do step #7. What this does is discharges all the solenoids is the car and returns them to base, clears the what I call "How you drive" memory. OH and reset your "MPG" every time you drive for the next 100miles.
You are being very vague with your directions. Upon first glance, I thought you were talking about shorting the battery. Do NOT short the battery, anyone, unless you want your battery to catch fire/explode.

If you're talking about an ECU reset, all you need to do is disconnect the terminals and hold the brakes down for about 10 seconds (the juice that is left in the system is dissipated via illuminating the brake lights).

While number 7 is important, the ECU will eventually work it out if you decide to start driving right away, but it will take much longer than just letting the car idle for 10 minutes.

I remember people used to do this to try and get more performance, but your ECU is constantly monitoring your driving habits and adjusting continually; it's not like it does this relearning for 100 miles and then stops.
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Old 10-10-2012, 05:08 PM   #19
Pickler
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Quote:
Originally Posted by chazly413 View Post
You are being very vague with your directions. Upon first glance, I thought you were talking about shorting the battery. Do NOT short the battery, anyone, unless you want your battery to catch fire/explode.

If you're talking about an ECU reset, all you need to do is disconnect the terminals and hold the brakes down for about 10 seconds (the juice that is left in the system is dissipated via illuminating the brake lights).
my mechanic already did all of that to reset the ecu and my MPG did not change. this was back in june and i think by now the computer would have learnt to be as aggressive as possible because i try to go WOT at least once for every 30min of driving. my biggest concern is MPG though. being a student, im paying 140$ a month for gas which is near my budget's limit for transportation expenses. i do mostly city driving because my car uses 1 liter more gas if i take the highway to college instead. my corolla used half the gas the impreza does on the highway but almost the same in the city. so that's why i am in a WTF state, i thought highway driving i could average 30mpg but apparently not. i wanted to use some hypermiling tactics but it makes the drive boring, eve still i have started coasting more.

Last edited by Pickler; 10-10-2012 at 05:14 PM.
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Old 10-10-2012, 05:19 PM   #20
Counterfit
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Draft trucks and large SUVs. You don't even have to get dangerously close for a benefit.
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Old 10-10-2012, 05:30 PM   #21
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Holy **** I am jealous of your guys gas mileage!!!!!! I averages 21mpg Stage II on my last tank.
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Old 10-10-2012, 05:37 PM   #22
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Quote:
Originally Posted by 03boxer4 View Post
Holy **** I am jealous of your guys gas mileage!!!!!! I averages 21mpg Stage II on my last tank.
I avg 19 ....this includes highway driving ..stg 2 sti with a car that dumps fuel stupid e tune
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Old 10-10-2012, 06:16 PM   #23
03boxer4
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Quote:
Originally Posted by Shortpersonbk View Post
I avg 19 ....this includes highway driving ..stg 2 sti with a car that dumps fuel stupid e tune
yea this mostly hwy as well I usually avg 20.
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Old 10-10-2012, 06:19 PM   #24
Counterfit
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I've been getting 21 since I got my car back from the body shop in June. Prior to that I was getting 23-ish even on the rich-ass stock tune. Coming back from Bretton Woods, I made it over 30 thanks to aforementioned snowmobilers doing 80 on 93S.
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Old 10-10-2012, 08:51 PM   #25
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Im averaging 18.9 MPG 100% city with a 2.5i.....
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