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Milage ... Gage ... Gas ...

Discussion in 'Gen 2 Prius Fuel Economy' started by Zeppo Shanski, Feb 13, 2019.

  1. Zeppo Shanski

    Zeppo Shanski Active Member

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    OK ...

    My trip-odometer says I've gone +/- 200 miles. The consumption screen says +/- 40 mpg. I'm figuring that should be ... lets say ... 5 gallons of gas ... from an 11.9 (I think) gallon tank. Why the hey does my gas gage on the screen only have two(2) little boxes left?!?

    I don't get any bonus points if I don't buy at least 10-gals. a pop.



    PLEASE HELP!!
    THANK YOU.
     
  2. fuzzy1

    fuzzy1 Senior Member

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    Your Gen2 fuiel tank has a inner flexible bladder, quite unlike the rigid tank of virtually all other cars. This bladder has long been a source of refilling problems and reduced capacities and numerous gauging consternations, especially in cold weather. It was a great concept (for evaporative emissions control) whose time had not yet arrived, so it was not carried over to the Gen3.

    While the theoretically capacity is 11.9 gallons, many Gen2 drivers find significantly less usable capacity. Even for those with no problems, driving to the very last low fuel warning uses only 9.something gallons, the same as with the non-bladdered Gen3 tank. The rest is set aside as a safety margin. But in a Gen2 you have no assurance that any margin is actually there. Test that margin at your own risk, consider taking along a can of spare fuel.

    Very many Gen2 drivers must give up on a possibility of 10-gallon bonus points because of that troublesome fuel tank bladder.
     
    #2 fuzzy1, Feb 13, 2019
    Last edited: Feb 13, 2019
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  3. Zeppo Shanski

    Zeppo Shanski Active Member

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    OK ... So are you telling me to get gas?
     
  4. sam spade 2

    sam spade 2 Senior Member

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    Even if he isn't saying that, I AM.

    There is no other way to see which meter is off by more than a little.
    And the "consumption" screen you are looking at must be consumption ONLY over that 200 miles since the last fill.

    If it is a long term average, it is meaningless in figuring short term usage.

    Most likely it is the gas gauge that is off. Most of them are somewhat unreliable, regardless of the make, model or tank type.
     
  5. audiodave

    audiodave Active Member

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    Just don't push it to far past empty. I've driven 40 miles after empty just for pump to shut off at 9 gallons next fill up. So you have gas just way tank and gauge work.

    Posted via the PriusChat mobile app.
     
  6. bisco

    bisco cookie crumbler

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    best you can do is go 400 miles and assume 10 gallons. but only if you know it's full to start, which you don't, so you're between a rock and a hard place.
    i was happy to trade up to gen 3 and get a real gauge/tank, but unfortunately, you get other problems gen 2 doesn't have
     
  7. Zeppo Shanski

    Zeppo Shanski Active Member

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    Swell.

    Seriously ... Thanks everyone for all your input commentary.
     
  8. fuzzy1

    fuzzy1 Senior Member

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    That is for the good ones, which are reasonably common. But some bad ones have suffered fuel starvation with 2 bars still showing, and having burned only 7 gallons.
    If you are not prepared and equipped for testing low fuel with a possibility of running out -- yes, fill up now.
     
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  9. Zeppo Shanski

    Zeppo Shanski Active Member

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    As it turned out ... I stopped for gas on the way home from work. I put in +/- 6-gallons. The mileage and distance shown seemed right. The problem so-it-seems is with the gas gage. It was down to one(1) box when the tank had some 4-5 gallons left. What the what is up with that? Suckamundo.
     
  10. Mendel Leisk

    Mendel Leisk Senior Member

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    You're making the assumption the tank capacity is per spec, when (as pointed out above) the internal bladder may have contracted some, reducing capacity.
     
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  11. fuzzy1

    fuzzy1 Senior Member

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    Most of those gallons are air between the bladder and tank wall, not fuel inside the tank.

    This is one of the reasons the evaporative control bladder concept was not continued in the next generation. A good idea whose time has not yet arrived.
     
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  12. Mendel Leisk

    Mendel Leisk Senior Member

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    Seems like the guys that did the bladder tank took a hiatus with gen 3, then came back for gen 4, designed the premature closing gas flap.
     
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  13. sam spade 2

    sam spade 2 Senior Member

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    It is a BAD design.
    Well known in the Prius owners community.
    Now YOU know too.
     
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  14. Zeppo Shanski

    Zeppo Shanski Active Member

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    LOL @ Me I guess.

    Thanks for clueing me in.
     
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  15. George W

    George W Active Member

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    As I'm in the market for a second Prius, a Gen 3 is on the consideration. I'd be interested in a sidebar of your experience in that matter. Thanks.
     
    #15 George W, Feb 15, 2019
    Last edited: Feb 15, 2019
  16. Zeppo Shanski

    Zeppo Shanski Active Member

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    OK ... After all that good information ... I've got another question ...

    I guess auto-shop class has changed a whole lot since the '70's. I've read a whole lot of threads/posts here all about oil and oil changes. Can someone please explain to me about how oil levels and viscosity make all so much of a difference in mpg. I thought I knew about things ... but you guys are talking some new type rocket-surgery as far as I'm reading.




    TIA for some help here.
     
  17. audiodave

    audiodave Active Member

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    Thicker oil requires more energy so hence less economy from the engine.

    Posted via the PriusChat mobile app.
     
  18. sam spade 2

    sam spade 2 Senior Member

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    It is mostly hype. Thicker oil doesn't move around as easily so there is a tiny little, slight difference in the amount of energy wasted inside the engine.

    Using a thinner oil also allows for tighter machine tolerances, which generally makes for a more efficient engine.

    The total difference due to the thickness of the oil itself might be.........a couple of gallons A YEAR.

    What do you mean by "oil levels" ?
     
  19. Zeppo Shanski

    Zeppo Shanski Active Member

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    Thanks.

    I understand completely about viscosities. If that was all it was then all cars would be running on strait 0 weight. New cars today have much closer tolerances than new cars of only 30-years ago. On top of that ... old cars with lots of miles need higher viscosities because they are much more loose than today's new cars. My questions are based on the multiple "Oil Change" threads where guys talk about such big problems as using 5-30 instead of "Toyota Recommended" 5-20. Then there is the big issue of 3.5-qts or 3.7-qts or 3.9-qts (as recommended) and ... God forbid ... 4-qts. NO ... I AM NOT SAYING THAT YOU SHOULD USE TOO MUCH. ... But one-tenth (1/10) of a quart is only 3.2 ounces. That will not cause any engine to blow. Other guys have mentioned that all of this effects the mpg in some way. Sure ... clean oil lubes better than dirty oil. My training and experience says that cars with lesser amounts of oil should be changed more frequently than cars with greater amounts. 4-qts vs 7-qts. The reasoning behind this is that we're dealing with internal-combustion engines. Fuel being burned up in the engine produces waste. Maybe it's only a little bit ... but it's still there. The oil gets dirty and the filters only hold so much. I'll spend oil change $$ every time over engine rebuild $$$. I'm not trusting the engines of my wife's car or mine with a 10,000-mile oil change.
     
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  20. sam spade 2

    sam spade 2 Senior Member

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    It is OCD. It is a disease.
    Seems like people HAVE to have something to worry about these days.........and if there is no real threat, they make up one.