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MFD and Calcuated MPF differs big time!?

Discussion in 'Gen 2 Prius Fuel Economy' started by tazman, Aug 9, 2006.

  1. tazman

    tazman Junior Member

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    Hi all, just put in my second tank. Had 444 miles and put in 7.21 gallons. Stopped it sooner this time since it spit gas back at me the first tank I filled. The MFD had 49.7 mpg, but my calc said 61.44. What's this all about? I know the full bladder can change sizes, but here in Hawaii the temps are pretty much steady. I put about 1 gallon and a half more after the pump first cliked off. Any ideas on this would be appreciated. I'm not complaining as 49.7 is WAY better than my other car got. Thanks. :rolleyes:
     
    #1 tazman, Aug 9, 2006
  2. tumbleweed

    tumbleweed Senior Member

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    I would suggest just going with the MFD number. Your bladder is still new and may expand and become more flexible with use. You could also try checking it over several tanks, instead of just one, to minimize the error.
     
    #2 tumbleweed, Aug 9, 2006
  3. hdrygas

    hdrygas New Member

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    <div class='quotetop'>QUOTE(tumbleweed @ Aug 9 2006, 02:32 PM) [snapback]300422[/snapback]</div>
    I think a 3 tank average is about right. Smooths out the ups and downs.
     
    #3 hdrygas, Aug 9, 2006
  4. Tideland Prius

    Tideland Prius Moderator of the North
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    Yup... average it out. Also, the bladder is expanding and loosening up as you refuel every time.

    I remember last year after my first road trip with the car. It took in 7 gallons and I had 4 bars left and travelled 400kms! I thought the pump was faulty but turns on that tank became my record tank haha.
     
    #4 Tideland Prius, Aug 10, 2006
  5. molgrips

    molgrips Member

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    I always seem to get 2mpg more when I calculate at the pump than the MFD says. Then again, I DON'T have the bladder so my situation is different. Anyone else out there driving without a bladder get the same situation?
     
    #5 molgrips, Aug 10, 2006
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