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Math Help

Discussion in 'Gen 3 Prius Fuel Economy' started by LRKingII, Jun 11, 2010.

  1. LRKingII

    LRKingII New Member

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    Here's the question.
    Reg E10 87 oct gas at $2.85 a gal right now.
    MPG on road trips with reg E10 gas = 48 calculated.

    Premium 91 oct straight gas "no ethanol" at $ 3.20 gal.
    What mpg would i need to get to make it worth trying a tank of the 91 oct no ethanol?
    Is it even possible to increase it?
     
    #1 LRKingII, Jun 11, 2010
  2. SureValla

    SureValla Member

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    sorry man too many unknowns
     
    #2 SureValla, Jun 11, 2010
  3. Dan bo

    Dan bo Prius Fan

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    Well to get the same ratio you would need 53.89 mpg.

    Will you get than going to 91??? I have no idea and doubt it is worth it.
     
    #3 Dan bo, Jun 11, 2010
  4. hyo silver

    hyo silver Awaaaaay

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    The price difference is 12%, so you'd need to see 54mpg or better to make it worthwhile. But does mileage increase with premium? I seem to recall that it doesn't, at least with the iconic version.

    If I'm wrong, I'm sure someone will correct me. ;)
     
    #4 hyo silver, Jun 11, 2010
  5. mainerinexile

    mainerinexile No longer in exile!

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    Is premium gas 'ethanol free'? I didn't think so.

    You won't get better gas mileage from the premium chemistry, but if it is actually ethanol free, you might get 4-5% better mileage according to what I've read. Still not cost-effective.
     
    #5 mainerinexile, Jun 11, 2010
  6. LRKingII

    LRKingII New Member

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    We have a local station the sells straight gas 91 oct NO ethanol in it.
     
    #6 LRKingII, Jun 11, 2010
  7. JimboPalmer

    JimboPalmer Tsar of all the Rushers

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    I have been assuming that the Prius ECU treats ethanol as filler.
    For most cars 10% ethanol should result in 3% less mileage
    In the Prius it seems more like 10% less mileage
    To make Premium 'worth it' you need over 12% better mileage
    12% more than 48 MPG is 53.895 MPG
     
    #7 JimboPalmer, Jun 11, 2010
  8. JimN

    JimN Let the games begin!

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    You'll probably get a bigger increase by inflating your tires to max. sidewall pressure and when it is cold blocking the grill.
     
    #8 JimN, Jun 12, 2010
  9. jdenenberg

    jdenenberg EE Professor

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    First, Ethanol is not a filler. It just contains 30% less energy than gasoline so E10 loses about 3%.

    Second, you will actually get slightly poorer MPG with Premium assuming the same ethanol content.

    So using Ethanol-free 91 octane will not quite make up for it's cost differential.

    JeffD
     
    #9 jdenenberg, Jun 12, 2010
    1 person likes this.
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