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Old 04-10-2012, 12:35 PM   #376
pxpaulx
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Originally Posted by RxMPLS View Post
I don't have PZEV and my first few miles are also really bad, typically. They're a little better when it's warm outside, though (or at least the poor mileage at startup lasts less time).

My mileage really dropped this weekend due to constant, strong, gusty, continuous headwinds (30 - 40 mpg) on my long drive yesterday. I think it went from about 33 to 28 mpg.
If yours is operating similarly at start without the PZEV maybe it is something they could update for everyone...I'm sure we'll have to wait months or even close to next year's updated release to get a change though.

Interestingly I drove most of my miles this weekend at the windiest times and still held a relatively high mpg average. Saturday afternoon drive from savage to little canada and back (via 169/35w/36/35e same return route...local highway numbers for another local!). Then on Sunday drove from savage to hastings across hwy 42 (direct, no interstate), then back west to savage on the same route into the 20mph winds (at about 4pm, probably the windiest of the day). I probably average 3-4mph slower than I would normally travel on this last portion, but other than that I drove pretty much normally and managed to keep the mpgs up.

Like I said though I'm not really complaining about my overall MPG, just that the cold-start engine warm-up time seems to be deliberately drawn out by the cpu warm-up process (I guess not completely attributable to the PZEV!).
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Old 04-10-2012, 08:48 PM   #377
BryanP5555
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Originally Posted by pxpaulx View Post
Bryan

Instead of saying you paid 3.96 a gallon and paid 53.74, it'd probably be easier to just say how many gallons were purchased! Also, If I divide 53.74 by 3.96 I get 13.57 gallons - did you buy anything else in the gas station? If not, then 13.57 gallons over 319 miles comes to 23.51 mpg.
true but i forgot to look at gallons i put in. i only knew cause i check my bank account.. also fuel range said i had another 40mile left till empty i added that to get the 26.666 or what ever it was
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Old 04-11-2012, 11:35 AM   #378
Tjohns
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Default MPG calculation

My previous vehicle (09 Silverado) displayed average and instantaneous MPG. What I understood about that system is that the fuel rate is calculated from the MAF sensor. Given the amount of air that is flowing, the computer delivers a precise amount of fuel to the engine. So now that the fuel rate is known, it can be divided by speed to read out instantaneous MPG.

In order to display average velocity I would suspect that the the computer samples the instantaneous MPG every few seconds or so and then averages them. When the car is motionless but running, MPG is 0.0 or in Suby's case the display reads ---.- null. This is probably not being averaged as it would drive the average MPG low.

This would explain why the average MPG on the computer is higher than the MPG calculated by dividing total miles by a tank of gas. The computer average should be closer to the EPA estimate because that test doesn't include idling time.
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Old 04-11-2012, 02:15 PM   #379
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^^ good point
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Old 04-11-2012, 02:24 PM   #380
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interesting hypothesis.

but as i thought about it, i think this is not correct. i've seen my mileage drop in my garage when the car was idling/warming up.(i don't sit there long, but it did drop in the 10 seconds or so i had it there when i had a pretty full tank).

so i'm guessing that the car measures how much fuel is actually being pumped into the injectors, but this purely a guess.

Quote:
Originally Posted by Tjohns View Post
My previous vehicle (09 Silverado) displayed average and instantaneous MPG. What I understood about that system is that the fuel rate is calculated from the MAF sensor. Given the amount of air that is flowing, the computer delivers a precise amount of fuel to the engine. So now that the fuel rate is known, it can be divided by speed to read out instantaneous MPG.

In order to display average velocity I would suspect that the the computer samples the instantaneous MPG every few seconds or so and then averages them. When the car is motionless but running, MPG is 0.0 or in Suby's case the display reads ---.- null. This is probably not being averaged as it would drive the average MPG low.

This would explain why the average MPG on the computer is higher than the MPG calculated by dividing total miles by a tank of gas. The computer average should be closer to the EPA estimate because that test doesn't include idling time.
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Old 04-11-2012, 06:50 PM   #381
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Default first tank

I was pleasantly surprised that my Sport M/T PZEV achieved 25.66 calculated on the first tank, display showed 27.4. It was a good mix of fun on cloverleafs, and 30/70 city /highway. I will say that the STI rear sway bar seems to ave a substantial impact on body roll. I bought this for the fuel mileage, but really enjoy the car so far in every other aspect as well.
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Old 04-11-2012, 11:46 PM   #382
AZFirstSubaru
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Default First fill-up

I have a 12 Impreza Sport Limited that has 460 miles on it. I just filled up for the first time and here are the numbers I got:

417 miles
32.4 mpg from display
30 mpg calculated
43 average speed

I was not kind to my car for the first tank. I couldn't resist testing the CVT with some jackrabbit starts, and I took it up into the mountains east of Phoenix to see how the AWD handled them.

I have a 47 mile all freeway commute. The drive home was at 37mpg, running about 70-75.

My Impreza replaces an 04 Cavalier, so the mileage increase really makes me smile.
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Old 04-12-2012, 01:20 PM   #383
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Default MPG calculation

I received this response from SOA regarding MPG calculations. I like this geeky type of information.

"Here is the available information on the Average Fuel Consumption indicator in our new vehicles, including our 2012 Impreza models. This information was provided by our Product Management Department

The information display, including the average fuel economy indicator, uses Local Area Network (LAN) and Controller Area Network (CAN). These systems connect the high speed inputs and outputs of various vehicles systems together with each other. This provides high speed communication between the engine and other vehicle systems to the information display. The inputs the system uses to calculate average fuel economy are: vehicle mileage, calculated distance from vehicle speed (odometer), and fuel injector duration, which is how much fuel is coming out of the injector based on time."
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Old 04-12-2012, 01:36 PM   #384
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Default MPG update and update from dealership on MPG

I emailed my dealearship on Monday about the MPG based upon what the service department had told me last week. No update from SOA, they told me to wait until May at which time they might have more information. I might follow up with SOA directly to see if they have anything to say (although I doubt it).

However, I do have some good news to report and that is that for the current tank I am on I have been doing "micro" trip readings (resetting trip B for legs of my daily commute). In certain in city driving situations I am able to get 29-30 (according to the trip computer) so likely 28-29 in reality. For example my 11 mile commute to work that includes dropping off kids at 2 different schools I was able to get 31 on the trip computer Tuesday and 29.1 today. The traffic was a little worse today.

The weather in Seattle has gotten significantly warmer starting last Saturday so that may have something to do with this.
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Old 04-12-2012, 02:40 PM   #385
pxpaulx
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FWIW, I didn't start seeing notably better numbers until my oil change at about 3200 - it did warm up, but has been colder the last week with temps in the low 30s in the morning - despite the lower temps the car has been holding an average of 33.3 all week. I'm about 260 miles into this tank and only one tick below half (last tick dropped off between 242 and 245 miles), seems to be about the best tank so far.
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Old 04-12-2012, 03:24 PM   #386
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Mostly freeway driving got me 31 mpg one time, and daily commute gets me about 27 mpg mostly, based on gas station receipts and OD (1917 right now.)
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Old 04-12-2012, 10:37 PM   #387
pxpaulx
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Originally Posted by dorkbert View Post
Mostly freeway driving got me 31 mpg one time, and daily commute gets me about 27 mpg mostly, based on gas station receipts and OD (1917 right now.)
That was my experience for the first 2500 miles or so, hopefully you'll have the same upward trend I'm having!
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Old 04-12-2012, 10:51 PM   #388
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Originally Posted by BIGD070572 View Post
I was pleasantly surprised that my Sport M/T PZEV achieved 25.66 calculated on the first tank, display showed 27.4. It was a good mix of fun on cloverleafs, and 30/70 city /highway. I will say that the STI rear sway bar seems to ave a substantial impact on body roll. I bought this for the fuel mileage, but really enjoy the car so far in every other aspect as well.
where did you get the sway bar and how much was it? Imo every car I have ever owned has had an undersized sway bar. I don't think my tundra even has one
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Old 04-12-2012, 10:55 PM   #389
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Is the PZEV supposed to get worse/better/same mileage? Is performance affected at all?

I had a Magnum SRT8 and the avg. mpg was usually 1 or 2 high. The Tundra is SPOT ON with-in .2 mpg 95% of the time. The only time it is off is if I do all highway. It actually reads 1 or 2 mpg lower than what I calculate. City driving is scary accurate though.
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Old 04-12-2012, 11:35 PM   #390
thom52
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Unhappy

CVT hatch, manually calculated "mixed mileage" on the first tank after hitting 1000 miles is 21.9 mpg.

Thats a lot of excuses that have to be overcome to reach the EPA mixed 30mpg. Of course if you consider "mixed" to be mostly long, full-speed freeway commutes, with a tiny bit of easy city driving tossed in, I suppose you could be a lot closer.

This car is miserable gas mileage in City driving.

Sorta hard to impress people with 21.9 mpg when they ask what mileage we get from our new tiny "high mileage" Subaru Impreza. My Honda Element is doing better at the moment.
My wife is pretty disappointed. Likely we would have gotten something else if we knew it was going to be so far off from its EPA rating.

Its definitely a LONG Commute, Freeway Trip car. period.

Or its a fun to drive car if you don't care about the mileage. We are fine with the CVT. No complaints there. Not sure why so many people are whining about the CVT.
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Old 04-13-2012, 12:00 AM   #391
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How is it even possible to get 22 mpg mixed? What kinda gas are you using, is the air filter clogged, are your tires flat, are you driving like a mad man?
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Old 04-13-2012, 02:14 AM   #392
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Quote:
Originally Posted by RoyB
How is it even possible to get 22 mpg mixed? What kinda gas are you using, is the air filter clogged, are your tires flat, are you driving like a mad man?
It's VERY possible if you have lots of short city trips & cold temps. I easily can get 36 highway on the first leg of a tank & watch the numbers nose dive as you add in city driving (hard city, shorter trips than EPA city is based on). Even with half highway the short city trips are killing my numbers too. But we're not the norm. Makes me believe there's something wrong with the car & me & my dealership are trying to present this info to SOA to get a response. I drive to maximize mileage, not like an ass, all other factors have been checked. I'm in nearly the same boat as Thom52. I'm Sleepnmnky on fuelly too. At 3600 miles I'm up to a whopping 23.5 on my last tank. =/

Last edited by SleepNMnky; 04-13-2012 at 02:41 AM.
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Old 04-13-2012, 02:19 AM   #393
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i have about 750 miles on the clock. i have been doing nothing but city driving. i did do 80ish miles freeway on this tank but i attempted to calibrated my MPG gauge but didnt know it was only for canada models and ended up resetting the trip. but only city and i am getting 29.1 mpg or probably 27ish with is dead on with the epa. my driving habit are "ignore it" while accelerating but feather the hell out of it while cruising city.
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Old 04-13-2012, 08:33 AM   #394
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Originally Posted by pxpaulx View Post
FWIW, I didn't start seeing notably better numbers until my oil change at about 3200 - it did warm up, but has been colder the last week with temps in the low 30s in the morning - despite the lower temps the car has been holding an average of 33.3 all week. I'm about 260 miles into this tank and only one tick below half (last tick dropped off between 242 and 245 miles), seems to be about the best tank so far.
Hmm, I had the opposite happen. I was finally averaging 30.0 on my commute and the temp dropped and my gas mileage dropped, last tanked my gauge read 32.7 so far this week 30.3, so I'm losing about 2.5mpg just due to the cold morning commute. When I left for work wednesday it was 24 deg. That drive to work dropped it down to 28 something, but it climbed back on my way home since it was warmer. Darn, I was hoping it was more of break in thing than a cold thing. I have 3500 miles on mine now and did an oil change at 2900. Also mine is not a pzev.
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Old 04-13-2012, 10:11 AM   #395
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Originally Posted by thom52 View Post
Not sure why so many people are whining about the CVT.


I see what you did there

I'm not currently going to post my mpg, as I'm still breaking in the engine, and doing so in a particular methodical way without beating on it.

Either way its much lower than anything I've seen so far, and I have just over 700 miles now...
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Old 04-13-2012, 10:59 AM   #396
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Imprzya, my car is garaged at night, so that might account for the difference - it is starting at least at 50 degrees or so.
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Old 04-13-2012, 11:23 AM   #397
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I've been frequenting hyper-miler wesites and forums and after carefully watching my driving I agree with a few of their pointers.
One is something I noticed myself in 5500 miles of mixed driving. The cruise control only gets you better mileage on flat ground. In hills I can modulate the throttle and read the terrain ahead better than the cruise control can. My mileage goes way down using cruise in the hills. This is exacerbated because mines a manual trans.
And after 500-1000 miles that engine is pretty much broken in. By the time 3500 rolls around the drivetrain has had time to break in as well. Then the mpg's really start to go up. Mine was better than the epa sticker new with 6 miles on the odo. Now its getting better than I ever hoped for.
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Old 04-13-2012, 11:31 AM   #398
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Originally Posted by pxpaulx View Post
Imprzya, my car is garaged at night, so that might account for the difference - it is starting at least at 50 degrees or so.
Mine is as well. You'd think starting out at 50deg the gas mileage wouldnt be so bad, but it is definitely affecting my car.
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Old 04-13-2012, 11:33 AM   #399
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Originally Posted by 79letour View Post
I've been frequenting hyper-miler wesites and forums and after carefully watching my driving I agree with a few of their pointers.
One is something I noticed myself in 5500 miles of mixed driving. The cruise control only gets you better mileage on flat ground. In hills I can modulate the throttle and read the terrain ahead better than the cruise control can. My mileage goes way down using cruise in the hills. This is exacerbated because mines a manual trans.
And after 500-1000 miles that engine is pretty much broken in. By the time 3500 rolls around the drivetrain has had time to break in as well. Then the mpg's really start to go up. Mine was better than the epa sticker new with 6 miles on the odo. Now its getting better than I ever hoped for.
I'm beginning to think that may be because you live somewhere warm
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Old 04-13-2012, 12:25 PM   #400
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I wasn't talking about weather. I was commenting on hyper-miler teqniques.
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