Good fuel.

Discussion in 'Prius c Fuel Economy' started by Javierz0509, Aug 11, 2017.

  1. Javierz0509

    Javierz0509 Junior Member

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    I used to put cheap fuel on my prius and i would get 50mpg highway and maybe 45mpg city, now since switching to Exxon i am getting easy 55 to 61mpg, not going back.
     
  2. fuzzy1

    fuzzy1 Senior Member

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    This MPG change is most likely not related to the particular brand of fuel you obtained.
     
  3. wjtracy

    wjtracy Senior Member

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    You got to give us some details, I assume E10 Regular.
    Florida is not reformulated gaso, so there could be some minor variations. I am expecting the greatest possible variation you could see is 7% or say from 50 to 53.5 MPG. Since MPG (energy content) is not a specification, it can vary, but the problem is you don't know what it is and there is no way to control it. If it was me I'd get samples in a gas can and measure the exact weight in grams per gallon. I would assume pump volume is correct. The more dense, the more energy. Since I live in reformulated gasoline area, we have essentially the same density in all brands and all grades, so I have stopped fiddling around with it
     
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  4. Mendel Leisk

    Mendel Leisk Lapsed Cargo Cultist

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    Just for giggles I filled up with Chevron 94, mainly because of this:

    [​IMG]

    I believe though in the States all the grades of ethanol? Anyway, extravagant expense for the high octane, but it's the one available way I have to dodge ethanol. So far so good, indicated mpg the best I've seen. But early days, I'll repost at the end of this tank.
     
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  5. fuzzy1

    fuzzy1 Senior Member

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    Most do, but it is not universal. It is still worthwhile for Americans to look.

    And even then, there will be unpredictable instances of scoring little or no ethanol when the 'may contain ethanol' label is present.
     
    #5 fuzzy1, Aug 11, 2017
    Last edited: Aug 11, 2017
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  6. roadrunner

    roadrunner His (blue) and hers (black).

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    Mendel Leisk,
    "I believe though in the States all the grades of ethanol? Anyway, extravagant expense for the high octane, but it's the one available way I have to dodge ethanol. So far so good, indicated mpg the best I've seen. But early days, I'll repost at the end of this tank."

    I would love to have that option in Pennsylvania (USA). Do you know how much that cost per gallon in US Dollars?
     
  7. wjtracy

    wjtracy Senior Member

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    Those of us living in reformulated gasoline areas basically cannot get E0. Others areas it is limited availability of E0. The ethanol mandate basically requires 10% ethanol in all grades, but companies can pay for credits if they want to sell some E0, and some smaller companies may be less encumbered by the mandates.
     
  8. wigmann

    wigmann Junior Member

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    there is an app called pure gas the will show you where E0 gas is available in your area.
     
  9. TheTimob

    TheTimob Member

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    I tried a tank of Shell 93 in my Prius C once, and measured a lower fuel economy over the course of that tank. But here's the thing: that was still E10. There's another fuel station near me that has some 91 octane E0, but it costs 45 cents a gallon more. I really don't think the potential increase of economy per gallon will translate to the lowest cents per mile to run the car, and that's what really matters to me in the end - cost per mile, not the highest MPG number.

    Ethanol gasoline has slightly less energy content per gallon than conventional forms of gasoline. That's why E85 Flex-Fuel ethanol vehicles get 20% lower fuel economy when using E85 instead of normal gasoline. Diesel has more energy content than gasoline does, which explains the higher average MPG numbers from Diesel cars. But we all know about what Volkswagen has done - it has pretty much permanently ruined the reputation of Diesels.

    But none of these tests are scientific at all, one tank is not enough to judge if the car is actually benefiting form differing octane. I would be very interested in more in-depth testing of fuels - I'm sure some members of these forms have tracked it to the detail of season/octane/ethanol content.
     
  10. Mendel Leisk

    Mendel Leisk Lapsed Cargo Cultist

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    The cost in US dollars would be kinda apples/oranges, since all gas prices are significantly higher up here. Maybe suffice to say, going from Chevron regular to to their (ethanol-free) highest octane, the (Canadian dollar) price (per liter) goes from maybe $1.31 to $1.54, a 17~18% increase.

    And so far, just getting into this tank, I'm guesstimating a 7~8% improvement in mpg. The big frustration for me: it's likely 7~8% ethanol in the regular, lol.
     
  11. wjtracy

    wjtracy Senior Member

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    That makes perfect sense. Higher octane does not necessarily equate to higher MPG, although that is one possibility. Yeah it's that 91 E0 where you might find better MPG because you know they didn't use ethanol to boost the octane, which means they might have done it the old fashioned way, putting more juicy energy aromatics in the E0. So you have a potential double whammy but still if your MPG went up +3 MPG, I don't think it ever comes close to paying off (with that market pricing structure).
     
  12. Mendel Leisk

    Mendel Leisk Lapsed Cargo Cultist

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    Hmm, so higher octane alone, more reluctant to ignite, may lower mpg. Also, take regular gas with ethanol, strip that ethanol out, you end up with gas below the recommended minimum octane, if I've got it right.
     
  13. wjtracy

    wjtracy Senior Member

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    Well. higher octane does not lower MPG because higher octane vapors are very easy to ignite with a spark. Higher octane fuel is only more resistant to "pre-ignition" before the spark occurs.

    Ethanol does have a fairly high octane, so yes taking out ethanol reduces octane. However, since octane is indeed a specification that must be met, if you take ethanol out then you need to have a higher octane E0 in the base fuel from the refinery. Typically but not always this is accomplished by increasing aromatics content, and aromatics have a lot of energy (+MPG). So your E0 95 Premium in Canada could be a really juicy fuel re: +MPG, depending on the manufacturing choices made at the refinery and your EPA-equivalent recipe mandates.

    I would expect 10% *maximum* difference in MPG (50 to 55 MPG) comparing USA E10 Reformulated Gasoline (which is a relatively low aromatics/low energy/low MPG) to your Canada E0 95 Octane. But you may not see the maximum difference all the time. Since in Canada you are not using USA refomulated gasoline in the base case, your advantage for E0 could be as low as +3% MPG (simply the ethanol effect).
     
    #13 wjtracy, Aug 13, 2017 at 11:22 AM
    Last edited: Aug 13, 2017 at 11:37 AM
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