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Winter gas and fuel trims

Discussion in 'Gen 3 Prius Main Forum' started by Spooled, Nov 12, 2018.

  1. Spooled

    Spooled Member

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    Is there any benefit to resetting the computer to optimize if for winter fuel? does it continue to "learn"? I also changed wheels so in my case maybe more beneficial to have the computer start over. Thoughts?
     
    #1 Spooled, Nov 12, 2018
  2. dubit

    dubit Senior Member

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    I reset the mpg history each summer/winter. Is this what your talking about?
     
    #2 dubit, Nov 12, 2018
  3. bisco

    bisco cookie crumbler

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    not that i have ever read
     
    #3 bisco, Nov 12, 2018
  4. Mendel Leisk

    Mendel Leisk EGR Fanatic

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    I think OP means to disconnect the 12 volt neg cable for a minute or so.

    I've done that when doing brake work, and the next few start ups (two or three), it does an unusual rev-up, for maybe 15 seconds. I'm thinking it's testing something, re-establishing some parameters.

    My 2 cents, I wouldn't bother doing this seasonally, but who knows.
     
    #4 Mendel Leisk, Nov 12, 2018
  5. ETC(SS)

    ETC(SS) The OTHER One Percenter.....

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    Ignore the MDF.
    Those values are only useful as an 'is/was' indication for relative fuel efficiency.
    The computer values are off by at least 3-percent.

    If you've changed wheel/tires then you're going to see a change in your fuel efficiency. That change will be reflected more or less as inaccurately by the MDF whether or not you 'reset the computer.'
    If I understand the ECU's role in dolling out gas to each of the four cylinders, I'm not sure what resetting it will accomplish other than to erase the information stored from the 'summer gas' use history.
    The only 'learning' that happens from what I remember is the DTE (distance to empty) guestimations which are updated by historical fuel efficiency guestimations.

    Either way, your car's 'real world' fuel efficiencies are not going to be affected by resetting the ECU if I understand life in Priuses correctly....whether or not your local fuel supplier has started diddling with your local formula.

    Does this happen on a specific date in Caly?
    Do they drain the tanks first or is the summer gas allowed to mix with the winter gas briefly?

    Winter versus Summer blends in the south east must not be that big a deal, because I never hear it discussed other than in this forum.....but my tank-to-tank averages in winter change more from temperature variations than fuel blends - and even then not by that much.
     
    #5 ETC(SS), Nov 12, 2018
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  6. Spooled

    Spooled Member

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    I too wonder if there i a "day" they change the formula, I have been meeting a lot fo refinery workers from socal lately, up in the bay doing a '"turnaround'" maybe thats it?
     
    #6 Spooled, Nov 16, 2018
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  7. Raytheeagle

    Raytheeagle Senior Member

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    Turn around is just an industry term for shutdown.

    They do a lot of repairs as downtime is $$$.

    I know the labor pool is thin up here as the turnarounds are happening.

    Not related to answer you question I would say though.
     
    #7 Raytheeagle, Nov 16, 2018
  8. bisco

    bisco cookie crumbler

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    there must be a required date in the law, but who knows when it gets to a gas station?
     
    #8 bisco, Nov 16, 2018
    Last edited: Nov 16, 2018
  9. Spooled

    Spooled Member

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    There should be a way to test it. Will return
     
    #9 Spooled, Nov 16, 2018
  10. Spooled

    Spooled Member

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    Boom! june 1 and sept 15

    We know that gas prices go up during the summer, generally around Memorial Day, but when do companies start producing these different summer fuels? The EPA defines April to June as the "transition season" for fuel production [Source: EPA]. Refineries switch over to summer-blend production in March and April [Source: EPA]. Gas stations have by June 1 to switch to selling summer-grade gas, while terminals and other facilities "upstream" from pumping stations have to switch by May 1 [Source: EPA]. Following the summer driving season, companies switch back to winter blends beginning in September, with the first winter increase in RVP allowance occurring on Sep. 15.
     
    #10 Spooled, Nov 18, 2018
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