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2002 Impreza AT
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17 Posts
Discussion Starter #1
Hi all! Please forgive my english. The wife and I bought our 2004 XT about two months ago and we've been enjoying it a lot. I decided to find out what kind of fuel economy I can get out of the car when driving very carefully, so I filled it up and reset the trip meter. We drove about 75% highway with the tank and 25% city.

Today I re-filled the car (the tank wasn't 100% empty but the needle was downright low) and here are the figures I'm getting:

I re-filled 43.66 Liters of 91 octane fuel (at 1.12$CAD/L)
The 'A' trip meter reads 670 km
So that means we traveled 670 km with 43.66 liters of fuel, resulting in 6.52 L/100km or 36 MPG.

Really? The economy of that car is THAT good!? I understand I am a very light-footed driver, I let go of the gas pedal as soon as I can in traffic, use the brakes intelligently on the highway etc. but I really wasn't expecting it to be so good, surely something is wrong with my trip meter? Or am I calculating it wrong? I used the calculators/converters on Opentoronto.com (sorry, can't post URLs...)

Someone please confirm if the trip meter on Foresters is known to give faulty results, or if the math of those websites is wrong. I'd like to get such good fuel economy when not soliciting the turbo, but surely this is too good to be true! Thanks :)

PS: The car has 82,800km on the odo, with stock tires.
 

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Administrator
2007 Forester Sports XT 4EAT
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Sorry, but something doesn't sound right.
43.66 liters = 11.5337518 US gallons
670 kilometers = 416.318699 miles
Seems likes a lot of miles, did you forget to reset it the last time you filled up? :confused:

Bobby...

['07 FSXT MODding Journal] ['03 X MODding Journal]
 

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Casper reincarnated
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Man oh man! I'd love to see those figures out of my N/A 03 XS. :biggrin:

I'm tend to agree with 2.5x_sleeper that the Trip Meter wasn't reset at the time of filling or indeed the trip meter is way out of whack.

Also a 6yr old car with only 82,000 kms on the clock sounds sus to me too. :icon_eek:
 

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2002 Impreza AT
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17 Posts
Discussion Starter #4
It's possible that I didn't reset the trip meter correctly, maybe I reset the 'B' meter by accident? That could explain it. Of course I'm sure I *did* reset it properly but mistakes happen. I reset it again when I re-filled so I will start the process over.

@Subyroo: Yup, and I have a stack of invoices from the Subaru dealer that gives me great assurance that it is legit. The car sure looks and feels like it hasn't been driven that much as well :)
 

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2004 Forester XT '06 STi 6MT
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707 Posts
Also a 6yr old car with only 82,000 kms on the clock sounds sus to me too. :icon_eek:
i bought my 2004 XT with only 26,900 miles on it (~16,700 kms) seven months ago. i even purchased it from the exact same dealer the original owners bought it from in 2004. flew down to colorado and drove it back to washington. too good to be true sometimes does happen :p

OP, i would keep checking the mileage over a broader range of driving. do it over more than a couple full tanks of gas too. on my drive back the day i bought my car i saw as high as 32 mpg on the freeway on cruise control at 70 MPH or less.

i don't think your MPG is outrageous though. light footed driving on turbo cars can equal very good gas mileage.
 

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Premium Member
2009 Outback XT-B 5MT
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10,254 Posts
I think you should try again.

The only time I've gotten over 400 miles, also almost used 16 gallons of fuel!
 

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04 XT
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I have found in my basically stock 04xt that traveling at 55mph nets better mpg in these short geared cars. I can only manage 24mpg and the car is all tuned up and running well. 24mpg comes out to 300 miles on a tank. What are peoples mods that are netting better MPG? I do have a K&N air filter...
 

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2008 Forester X Premium 5MT
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8,071 Posts
Also keep in mind that the speedo/odo may be off, if you have not verified them against a gps they are only good for rough numbers.

Was the same fuel pump used to fill the tank this time as the last time you filled it?

Was the car parked the same way as last time at said pump?

Did you fill up at about the same time of day(same temp), fuel expands with heat.
 

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2010 FXT Limited 4EAT Sport Shift
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Of course you know you can't always rely on GPS's to provide you with accurate distance readings....the constellation of satellites that provide the GPS with time signatures differ by the second/minute/hour/day/etc.
There must be somewhere nearby wherer the county/state/federal highway folks have mile markers, where you can compare your odometer/speedometer with actual measured distances.
To increase accuracy, do your test over say 5 or 10 miles, and average it out (if you're doing 60 mph, it should take you exactly 60 secs to encounter each mile marker).
-Quick

Also keep in mind that the speedo/odo may be off, if you have not verified them against a gps they are only good for rough numbers.

Was the same fuel pump used to fill the tank this time as the last time you filled it?

Was the car parked the same way as last time at said pump?

Did you fill up at about the same time of day(same temp), fuel expands with heat.
 

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Premium Member
2019 Crosstrek 2018 XT
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14,498 Posts
Of course you know you can't always rely on GPS's to provide you with accurate distance readings...
While its true that they very in position and the GPS will pick up different ones at any given time. In the composite they are accurate to about an inch.

I have never heard what you said to be true. If you have seen this information I would appreciate a link. Thanks.

To the OP. You need at least two tankfulls and need to fill the tank both times and start the milaeage reading with a full tank. I will typically get at least 2 mpg difference when calculating the mileage on 1 tank. You are probably 10 mpg off.
 

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2009 Outback XT-B 5MT
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Did you fill up at about the same time of day(same temp), fuel expands with heat.
Time of day doesn't matter. This is a myth. You can take this out of the fuel economy equation.
 

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2010 FXT Limited 4EAT Sport Shift
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Time of day doesn't matter. This is a myth. You can take this out of the fuel economy equation.
BAC5.2-
As one who used GPS's before they were available to the general public, when one had to perform 'mission planning', I have to disrespect your statement that time of day doesn't matter. Because the PDOP (position dilution of precision) of the constellation is constantly changing, to get accuracy 'to an inch', you have to pay attention to the PDOP. GPS's for automobiles don't get accuracies to the inch, to do that you need survey grade GPS systems (where differential correction is made with more than one transmitting GPS instrument).
If you have a handheld Garmin of any recent models, you'll see the graphics displaying a bar graph that constantly varies which constellation satellite is being used to maximize PDOP. Vehicle GPS's don't employ such efforts to obtain that level of accuracy/precision. Note that $500 Garmins will seldom get the 3 meter accuracy so often promised...only under ideal constellation configurations will you get that.
I'm sure you're aware that it takes 3 points to define a plane. It takes another point (total of four) to define a point in "time", and the spatial array of the satellites being accessed has everything to do with the PDOP. As you drive through a forested landscape or in a urban setting with structures that limit your horizon, you're also limiting your accuracy/precsion (yes I know accuracy and precision are different, but they're different sides of the same coin, and are both affected by the arrangement of satellites).

adc-
I have chosen the following URL as it can get you answers that range from simple to complex, and is from one of the premier GPS manufacturers in the range of users from civilian to military, from handheld to survey grade and better applications. Check out:
Trimble - GPS Tutorial

pleiades-
You work in the remote sensing/GIS/GPS arena...am I far off the mark?
-Quick
 

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2019 Crosstrek 2018 XT
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Good information Quicksilver. I know my first GPS about 12 years or longer ago got maybe 200 feet. My cheapie Garmin does do consistently maybe 10 ft. I know that repeatable results give my speed at 3% less than indicated gage reading. Mileage seem to be be very repeatable.

So not doubting your information but I'll take my GPS over indicated mileage on the Subaru. But his numbers are fubar anyways. :D
 

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2010 Premium MT
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32 Posts
Really? The economy of that car is THAT good!? I understand I am a very light-footed driver, I let go of the gas pedal as soon as I can in traffic, use the brakes intelligently on the highway etc. but I really wasn't expecting it to be so good, surely something is wrong with my trip meter? Or am I calculating it wrong?
I believe someone on this forum once adequately documented 35.3 mpg over 542 miles in a 2010 so ISTM your numbers are possible.

Nicely done, BTW.
 

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2016 Forester XT AT
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...

Also a 6yr old car with only 82,000 kms on the clock sounds sus to me too. :icon_eek:
Our van is like that, so if there is documentation to back it up, no worries.

And as for GPS data being accurate, I do nto trust it that much. I use a Garmin Map60C for my bush work and it will tell me that even though I am not moving, I am going 15 kph. Or that I have averaged 40 kph for the day, walking! I wish. Anyway, I have learned to take that data with a grain of salt. GPS is very good in showing you where you are in reference to other features, but the consumer grade units just don't do very well when showing true distances/speed etc. Now give me a Trimbal and we can see what it will do!
 

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2010 FXT Limited 4EAT Sport Shift
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35 mpg

J-F hasn't been back with a recount of subsequent tankfuls...let's see half of 36 mpg is 18 mpg, which is what I get when I go easy on the throttle...I think the real kicker is, who could stand to drive 542 miles with an egg between your foot and the throttle?
-Quick
 

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2005 Lifted 2.5 XT 5-Speed MT Dual-Range
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It's impossible. Unless he was driving these 542 miles downhill or he has a diesel engine or mpg calculated is imperial and not us.
I wouldn't say that it's impossible at all. It depends on the roads/driving style/temperature, altitude, etc. Whereas I can't get over 20 mpg in the city, when we drove up to Wolf Creek last year, I was averaging roughly around 32 mpg and we were going up and down hills and had the cruise on, snowboards on the roof basket, and the back packed full of gear. Speeds varied from 50-70 mph and there was snow on the road.

Right after the picture was snapped, we pulled over for gas in Chama, NM (the trip was at 110 miles) and I only managed to squeeze 3.4 gallons in...which comes out to a little over 32 mpg. I knew I could have probably yielded 35 if I was very careful, but I was already happy I was getting over 20. :biggrin:

 

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2009 XT
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I wouldn't say that it's impossible at all. It depends on the roads/driving style/temperature, altitude, etc. Whereas I can't get over 20 mpg in the city, when we drove up to Wolf Creek last year, I was averaging roughly around 32 mpg and we were going up and down hills and had the cruise on, snowboards on the roof basket, and the back packed full of gear. Speeds varied from 50-70 mph and there was snow on the road.

Right after the picture was snapped, we pulled over for gas in Chama, NM (the trip was at 110 miles) and I only managed to squeeze 3.4 gallons in...which comes out to a little over 32 mpg. I knew I could have probably yielded 35 if I was very careful, but I was already happy I was getting over 20. :biggrin:

x blue fox:
32 mpg is about 8,7 L/100 km. But 35,3 mpg is 6,7 L/100 km and that is a difference. The 32 mpg is the best i could get driving w/o any traffic and respecting the max speed of 80 kmph. Decreasing the consumption of another 2 liters/100 km with the car that weighs 1,5 tons and is aerodynamic like a brick is not possible in my view. Unless you really go down hill or have strong back wind or perhaps driving 40 kmph on a highway w/o any traffic(but that is not realistic).
 
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