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Does fuel economy affected by how much gas left in the tank.(full tank vs 3-4 bars)

Discussion in 'Prius c Fuel Economy' started by amilamad, May 9, 2015.

  1. amilamad

    amilamad Junior Member

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    I read somewhere that the fuel pump is inside the fuel tank and its best to keep the pump drown in fuel for better fuel efficiency. Is this true ?.

    And does the fuel pressure affect the economy?.
     
    #1 amilamad, May 9, 2015
  2. JimboPalmer

    JimboPalmer Tsar of all the Rushers

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    The pump is reported to last longer when always covered by the fuel, but I have no reason to expect better fuel mileage.
     
    #2 JimboPalmer, May 9, 2015
  3. valde3

    valde3 Senior Member

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    Pump will keep the pressure constant. So pressure will stay the same until there’s so little fuel in the tank that pump is sucking in air. Sucking in air will also shorten the life of the pump.

    So fuel economy will be the same regardless of amount of fuel in the tank. Except for the small effect that the weight of the fuel will have.
     
    #3 valde3, May 9, 2015
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  4. jdenenberg

    jdenenberg EE Professor

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    The only impact on MPG is the weight of the gas in the tank. You would find it difficult to measure the affect of the small additional weight.

    JeffD
     
    #4 jdenenberg, May 9, 2015
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  5. bisco

    bisco cookie crumbler

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    this is an interesting hypothesis, i read it somewhere as well.:)
     
    #5 bisco, May 9, 2015
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  6. wjtracy

    wjtracy Senior Member

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    Do I assume correctly this design is the same as all Prii at least Gen2+ ?
    We have had very few pumps replaced to my recollection.
    No mention of better MPG with fuller tanks from the experts (800 miles per tank crowd).
    Maybe this is one reason Toyota makes us fill the tank with still 2-3 gallons when the pip starts blinking
     
    #6 wjtracy, May 9, 2015
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