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MPG Musings

Discussion in 'Gen 2 Prius Fuel Economy' started by jimgraffam, Feb 16, 2006.

  1. jimgraffam

    jimgraffam New Member

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    Hi folks. Several thoughts... all related to MPG. Some just observations plus one genuine question

    I'm sure all my fellow New Englanders have noticed the warmer weather we've experience. Wow! What a difference 20 degrees makes. Two tanks ago was a great tank and I'm working on a great one now... currently almost 56mpg all week long over the hill 'n' dale of Rt. 2.

    I admit that I was skeptical at first, despite the overwhelming concensus of the forum, but I think I might just be a "believer" of the mystical breakin period now. That first really good tank was in good weather but it also was just after crossing 3,500 miles.

    Genuine question: Is Shell gas really bad? In an unusual move, I fuelled up nearer to work last week and consistently had to fight to keep the MFD readout about 50 mpg... actually computed in the 40s for that tank :( I don't believe I changed my driving habits over that time... and certainly not that dramatically. And the weather was also unseasonably warm too (I stayed home during the blizzard... no contribution from weather there).

    Thoughts?
     
    #1 jimgraffam, Feb 16, 2006
  2. Maytrix

    Maytrix Member

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    This warm weather is really starting to piss me off! It's January! And we get more snow in MA then they do in the mountains!

    As far as gas - I haven't really noticed much of a difference that I could equate to filling up at different stations. I'll admit I don't fill up at Shell stations much though.
     
    #2 Maytrix, Feb 16, 2006
  3. paprius4030

    paprius4030 My first Prius

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    I know they're all supposed to be the same, but I seem to do a little better with Exxon.
     
    #3 paprius4030, Feb 16, 2006
  4. jimgraffam

    jimgraffam New Member

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    :D Don't want to burst your bubble... but it is February...and almost March.

    Bring on the warm weather!

    This was my first time really noticing an unexpecte 'hit' to the MPG. Needless to say, I don't expect that I'll be fuelling there again anytime soon. Maybe they have more winter additives or something?
     
    #4 jimgraffam, Feb 17, 2006
  5. Maytrix

    Maytrix Member

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    LOL, I really meant February. And yeah, it's almost March and snowmobile season is looking like it will be over before it's even started. Skiing hasn't been terrible, but things could be better there too. I really feel bad for all the business in the Northern half of NE - They are all taking a huge hit and I'm sure a number will go out of business because of it.
     
    #5 Maytrix, Feb 19, 2006
  6. keydiver

    keydiver New Member

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    I was analyzing the mpg data that some of the guys have posted, and it seemed that there is indeed something good about >3,000 miles. All of them showed several mpg improvement once they passed that point. I'm at 1500, and I can't wait! :lol:
     
    #6 keydiver, Feb 20, 2006
  7. jimgraffam

    jimgraffam New Member

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    More musings...

    Ok. Here's my theory on my latest tank. MFD was 52.6 mpg / Calculated was 45.6!

    This is by far the biggest discrepancy between the two methods. I am hoping it is related to two contributing factors: (1) My Prius was not level at fillup and was slanted noticeably towards the passenger side and (2) the Prius was "warm" at fill up in about 40deg weather.

    I'm going to be optimistic and hope that this balances in the next tank with a higher than normal mpg... for now. :)
     
    #7 jimgraffam, Feb 23, 2006
  8. Catskillguy

    Catskillguy New Member

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    Maybe the crude is being sabotaged??? Royal DUTCH Shell ;)
     
    #8 Catskillguy, Feb 23, 2006
  9. Catskillguy

    Catskillguy New Member

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    Am I missing something as a newbie owner... Wouldn't the MFD mpg be the most accurate measure since that is somehow measuring the actual fuel going through the system and calculating vs the miles measured,...... while the fuel being pumped has soooooo many variables (temp, gas pump, angle of nozzle, speed of filling, angle of car, etc etc etc etc) to affect the amount of fuel that goes back in on a particular tank?????
     
    #9 Catskillguy, Feb 23, 2006
  10. tripp

    tripp Which it's a 'ybrid, ain't it?

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    That's the conclusion that I came to. Generally the two methods jibe pretty well but when there are wild temp fluxuations the manual method seems worthless. All of those other factors are hard to control as well. I still do a manual calculation but I tend to go with the MFD numbers. Those should be consistant.
     
    #10 tripp, Feb 23, 2006
  11. tripp

    tripp Which it's a 'ybrid, ain't it?

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    Varying amounts of ethanol blended in? Most places say that the "Gasoline dispensed from this pump contains up to 10% Ethanol". Just a guess. probably not a good one.
     
    #11 tripp, Feb 23, 2006
  12. jimgraffam

    jimgraffam New Member

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    I too have found general conformance between the two methods... with the manual method typically under the MFD. Though (I hope) temporarily annoying, I should think that the manual method should converge and normalize somewhere close to the MFD in the long run.
     
    #12 jimgraffam, Feb 23, 2006
  13. HybridVigor

    HybridVigor New Member

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    Same conclusion here. Seems to me that the only factors in play are A) Does the pump actually dispense what it says it dispenses? and B_) Does fuel injector #1 measure fuel accurately?

    My guess is that B is probably accurate (otherwise your engine would have trouble with the fuel-air mixture?) and that the pump is putting out 1-2% less than it reports. If MFD vs calc'd mileage evened out over time, then the difference is probably just tank-to-tank filling inconsistencies. Over the long run, there has to be some other reason, right?
     
    #13 HybridVigor, Mar 3, 2006
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