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2020 Outback Limited XT
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Discussion Starter · #1 ·
We started off with a full tank of gas Tuesday for a trip down the Crowley's Ridge Parkway. Went thru about 20 miles to catch RT 57 south at Kankakee. IL.It was a hot day, upper 80's and lower 90's with a bit of a moderate south wind. That's got to be the longest boring stretch of road ever. Filled up the tank in Sikeston, MO. Using the built in mileage in the Outback, don't know it's accuracy, it said I had gotten 25.2 mpg at mostly 75 mph. I was pretty pleased with that. I had a great meal of frog legs at Lamberts. If you have never eaten there try one if you get the chance. They toss hot rolls across the room if you want one, and come around and put food on your paper towel if it's something you want.
Spent 2 days driving down Crowleys Ridge AK which is a nice twisty road thru the country side.Went across to Memphis TN and spent the night. Filled up with a half of tank of Valero regular, I always use regular. The half tank was of a no name fuel I had gotten in Arkansas.
We headed home by going back into AK and taking rt 55 up to rt 57. It was another very hot day again in the 90's range, not much wind at all,I then checked the mileage with the built in system again. It said I was getting 30.2 mpg, again driving mostly at 75 mph. I had always heard good things about Valero gas, but there is none near where I live now days. I haven't check the mileage since as that's not what I usually do. I just wonder if it was the Valero gas that made my mileage better???
 

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The fuel quality makes a huge difference...filled up in new Mexico at Maverick station and look at what Subaru said I was getting...if you get an opportunity try some ethanol free fuel.
Car Speedometer Odometer Gauge Mode of transport
 

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Many factors need to be considered to determine if fuel is responsible for that much of a difference.

Did you take the exact same route both ways?

Was the air conditioning on all the time?

Are there more uphill elevation changes one way compared to the other?
 

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The fuel quality makes a huge difference...filled up in new Mexico at Maverick station and look at what Subaru said I was getting...if you get an opportunity try some ethanol free fuel.
View attachment 539260
This seems like best-case scenario driving conditions lead to this economy, not all due to the fuel. What are the circumstances behind this mileage compared to what you normally get and how your normally drive?
 

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2021 MGM Onyx XT
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I just wonder if it was the Valero gas that made my mileage better???
I'm going to guess that wind was a factor. We're familiar with those stretches of I-57 and I-55 and the wind always seems to being blowing briskly from the south.

At Christmas we drove from the Chicago area to Nashville and back on I-65. Fairly strong south wind on the way down and on the way back. Hand calculated mileage was 27.7 going down and 31.7 coming back. Same route both ways.
 

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Discussion Starter · #6 ·
Many factors need to be considered to determine if fuel is responsible for that much of a difference.

Did you take the exact same route both ways?

Was the air conditioning on all the time?

Are there more uphill elevation changes one way compared to the other?
A lot of it was the same.
Uhhh, it was in the 90's, of course the AC was on
Elevations was about the same.
 

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Discussion Starter · #7 ·
I'm going to guess that wind was a factor. We're familiar with those stretches of I-57 and I-55 and the wind always seems to being blowing briskly from the south.

At Christmas we drove from the Chicago area to Nashville and back on I-65. Fairly strong south wind on the way down and on the way back. Hand calculated mileage was 27.7 going down and 31.7 coming back. Same route both ways.
The wind was against me going down, not much at all coming back.
 

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2020 OB Limited, Titanium & Magnetite Grays
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The dash average MPG display seems to be ~5% optimistic as determined by a number of past postings and my experience with two Gen 6 Vehicles. There are many variables that can change the mileage, most of which can be found elsewhere in this forum. I will attempt to name a few:
  • Temperature of gas has an effect on mileage. A gallon of hot gas has less energy than than a gallon of cold gas.
  • Filling up with a pump that puts out a faster pump rate, new filter, will sometimes cause an early valve shut-off due to the short lived surface foam.
  • Know that most of our gas has been mixed in the shared pipelines after refinement. Each brand may later mix in their special additives. The suggested brand would have to have more energy per gallon to make a noticable difference in MPG.
  • Wind and altitude changes have an effect on MPG.
 

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2021 Outback Limited 2.5i Autumn Green
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It is also possible that your drive out had an overall positive elevation gain, and the more direct drive back had a net elevation loss. Also, did you mean AR (Arkansas) instead of AK (Alaska)? I’ve driven down to CO from AK and it definitely takes more than two days of driving 😆
 

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Discussion Starter · #10 ·
It is also possible that your drive out had an overall positive elevation gain, and the more direct drive back had a net elevation loss. Also, did you mean AR (Arkansas) instead of AK (Alaska)? I’ve driven down to CO from AK and it definitely takes more than two days of driving 😆
Ment AR, sorry.
 

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The dash average MPG display seems to be ~5% optimistic as determined by a number of past postings and my experience with two Gen 6 Vehicles. There are many variables that can change the mileage, most of which can be found elsewhere in this forum. I will attempt to name a few:
  • Temperature of gas has an effect on mileage. A gallon of hot gas has less energy than than a gallon of cold gas.
  • Filling up with a pump that puts out a faster pump rate, new filter, will sometimes cause an early valve shut-off due to the short lived surface foam.
  • Know that most of our gas has been mixed in the shared pipelines after refinement. Each brand may later mix in their special additives. The suggested brand would have to have more energy per gallon to make a noticable difference in MPG.
  • Wind and altitude changes have an effect on MPG.
I will second your third point. All fuel in one geographical area all comes from the same terminal (and the same pipeline). The only difference would be the amount of ethanol and the additives. In my area, nearly all the fuel is E10 so it's all the same stuff except for the additives. If you can find ethanol free fuel (E0), then that would have 3% more energy density than E10 on average.

In regards to temperature, most gas stations use underground tanks so the temperature is pretty constant and gasoline volume doesn't change much with temp anyway. I think the rule of thumb was that volume changed by 1% every 15 degrees. Maybe if you filled up at a station using above ground tanks, then you'd see some variability.
 

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2022 Touring XT, formerly 2005 LL Bean
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Headwind makes a significant difference. I just did a long trip, all flat terrain, all freeway. One day of headwind was 26.2. Opposite direction a couple of days later, no headwind, was 28.8. Refilled about 2 hours from home, just after a new headwind had picked up. Refilled at home before any city driving and that tank was 27.4. 2022 XT.
 
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