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MPG gauge 2012 hybrid models

Discussion in 'Gen III 2010+ Prius Fuel Economy' started by alfon, Nov 29, 2011.

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  1. alfon

    alfon Active Member

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    If a forum member buys a 2012 Toyota Hybrid model, either the Prius, Prius V, or Camry Hybrid, please let us know how accurate
    the MPG dash gauge is.

    As we all know on the 2010-11 Prius models the MPG gauge is off
    by about 3-4 mpg consistently on nearly all those vehicles.

    This is obviously no mistake but intentional on Toyota's part, so owners will think they are getting far better mpg's than in reality.

    So, I believe that the 2012 Prius V is more accurate and hopefully the 2012 Prius and Camry Hybrid will be as well.

    If they are more accurate it would be nice to see what they did to
    correct the computer error.

    alfon
  2. F8L

    F8L Protecting Habitat & AG Lands

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    A lot of other vehicles exhibit this error in mpg as well. Some worse some better. The GenII Prius was more accurate then the GenIII. Hopefully the newer cars will be more accurate. I tried making a thread for the v model but it seems the new guys are not following the format I set. Sooner or later they will catch on and report better data. I'll edit my post to emphasize the calculated vs. MFD mpg.

    Justin
  3. bisco

    bisco cookie crumbler

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    i would say our 08 hycam is fairly accurate. it's difficult to be exact since you don't know exactly how much gas you used.
  4. alfon

    alfon Active Member

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    Well the most accurate way, is to fill up your gas tank to the top of the neck so no more gas can be filled in the tank.

    Than drive to nearly empty, and fill up to the exact same place to the top of the gas tank neck, and if possible, the same gas station and gas pump.

    Record your mpg computer and record the miles driven and gallons used. A simple calculation with miles divided by gallons will give
    you your TRUE mpg.

    Now compare your TRUE mpg with the computer generated amount and compare the difference.

    alfon
  5. Rebound

    Rebound Senior Member

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    You should NOT do this. Emissions control systems in most cars ventilate the gas tank fumes through a canister of charcoal. If you overfill the gas tank, the liquid gasoline can enter these lines and cause damage. Just pump the gas until it clicks off. Any error in that will average out over a few fill-ups anyway.

    Otherwise, what you say is exactly right. As you can see in my signature, I track the gallons using Fuelly | Share and Compare Your MPG. I keep a link to Fuelly as an icon on my iPhone. When I get gas, I tap the icon and it takes me straight to a page that I can enter a fill up onto. The Fuelly website handles all the calculations, tracking every fuel consumption statistic imaginable.

    Here's a screenshot of the Fuelly entry screen from my iPhone:

    Attached Files:

  6. ecoprius

    ecoprius Junior Member

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    Thanks for the website info. I'm a new owner, I put 7gal in my car so far and was thinking of tracking my gas mileage data. I just signed up.
  7. Rebound

    Rebound Senior Member

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    Welcome to Fuelly! I've tracked over 24,000 miles and over 500 gallons of gas, for an average of 48 MPG. Over enough time, everything averages out :)

    When I began tracking mileage, I always filled at the same station until the pump clicked off the first time. Use the 87 (lowest) octane. Higher octane will reduce your mileage.

    Enter the gallons added and miles on your trip odometer. I also enter the price per gallon. I have 33,000 miles on my Prius, so I've tracked about 2/3 oft fill ups. (My wife won't do any of this, so of she fills up, I have to wait another fill up until I can track again).

    The Prius can display mileage histograms, the cool- looking engine/motor display, or the HSD, which looks like a sideways thermometer. It's the HSD display that lets you maximize mileage.
  8. Joe166

    Joe166 New Member

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    I don't see how higher octane can possibly lower mileage. It is a waste of money, but the only possible effect is a change in the timing to make use of that higher octane and that MIGHT improve but could not lower mileage. Do you have any scientific explanation of this phenomenon?
  9. macman408

    macman408 Devil's Advocate General

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    Yes; higher octane fuel contains slightly less energy per gallon.
  10. Joe166

    Joe166 New Member

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    Can you point me to something that supports that? Since most cars get higher fuel efficiency with higher octane IF THEY ARE DESIGNED FOR IT, I don't see how. But I am always willing to learn.
  11. Joe166

    Joe166 New Member

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    OK, I waited a couple of days for a response, then looked it up myself. The statement that higher octane fuel contains slightly less energy per gallon is misleading at best. From my admittedly unscientific research it would appear that SOME higher octane fuels MIGHT contain slightly less energy per gallon. The difference is negligible. Almost certainly not enough to cause lower mileage. Probably within the amount that driving habits or environmental differences would cause.

    That doesn't change the fact that using higher octane fuel than your engine is designed for is throwing money away.
  12. Rebound

    Rebound Senior Member

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    I tested this myself, and my mileage went down with higher octane gas. The reason, I was told, is this: Higher octane gas ignites at a higher pressure/temperature. High performance engines, especially V8's, compress the air/gasoline mixture more before firing the spark. This requires higher octane, to prevent pre-ignition. The higher compression produces more power (more gas/air ignite).

    So with Prius, the engine only needs 87 octane, and the higher octane gas therefore doesn't fully burn in the combustion chamber, which, I'm told, is why mileage goes down. Sounds plausible to me.
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