My 2018 Prius Three is draining gas FAST

Discussion in 'Gen 4 Prius Fuel Economy' started by Chime, Aug 31, 2018.

  1. Mendel Leisk

    Mendel Leisk Witness Leader

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    With Jalopnik links you need to type some text, highlight it, select the link button in editor, then paste the link.

    Direct pasting the link is the problem.
     
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  2. Classic Car Guy

    Classic Car Guy Active Member

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    Now where do you gas this up?
    Ford Pinto Beans.JPG
     
  3. alanclarkeau

    alanclarkeau Senior Member

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    2008 Focus had it on the RIGHT - 2010 Fiesta had it on the LEFT.
     
  4. alanclarkeau

    alanclarkeau Senior Member

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    You need to do a full fill (to first click) otherwise the Distance To Empty will be wildly inaccurate. You can't judge by just part of a fill. Fill it, refill it when at least 3/4 tank used and work out the average. You can ZERO the "TRIP A" (or B) with every fill and it'll give you an approximate figure. I think mine is using about 4.2 litres/100km - some do better, some a little worse. It largely depends on your driving style plus your environment.
     
  5. padroo

    padroo Senior Member

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    I didn't realize so many cars had the gas door on rheem right. My Plymouth Prowler has the door on the right and I have two ols GM cars with rear access. The article says they outlawed rear gas doors for safety reasons.
     
  6. dubit

    dubit Senior Member

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    I wondered why I never seen that on cars anymore (gas door on rear of car)
     
  7. El Dobro

    El Dobro A Member

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    The cap seals go bad or the cap is on wrong and the gas came flying out when you accelerated on the old behind the plate fillers. It also had the tank too close to the rear of the car, if there was a crash.
     
  8. fuzzy1

    fuzzy1 Senior Member

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    Here is a real world example of "Distance To Empty" anomalies, observed yesterday from my other vehicle (not a Toyota), thus with a different 'customer expectation management' philosophy.

    All these figures are from a single trip, on the same tank of fuel:
    TripA = 0 miles, DTE = 360 miles (Sum = 360); Start of trip, after some gnarly winter use and long warmups to clear overnight icing;
    TripA = 25, DTE = 320 (Sum = 345); downhill and up, very little net elevation change;
    TripA = 70, DTE = 460 (Sum = 530); after major valley descent;
    TripA = 310, DTE = 150 (Sum = 460). after several climbs and descents, and plenty of flat prairie. (Refueled here, before final trip segment).

    Notice that on this vehicle, DTE does not drop mile-for-mile by the number of miles driven, not even close. In fact, for one segment while driving 45 miles, the forecast distance remaining actually increased by 140 miles, thanks to some very high MPG while gliding downhill. But the next segment of 240 road miles ate up 310 miles off the remaining distance estimate.

    If DTE forecasts were accurate, then the Sum of TripA and DTE during any single trip would be a fixed constant. But I observed a 185 mile swing or variation.

    But this vehicle (a Forester) has very different display rules and 'customer expectation management' than the Prius. The Forester uses a much shorter recent driving history (60 km according to the Owners Manual, but I suspect it might be 60 miles), while the Prius remembers much more distance. The Forester allows its display number to rise when poor MPG conditions flip to great MPG conditions, but the Prius forbids this. In fact the Prius forces the display to fall at least 1 mile for every 2 miles driven, even when gliding down long hills without using any fuel. The only time the number is allowed to rise is when at least several gallons of fuel are added, just one gallon is not enough.

    Additionally, the Prius sets aside about 2 gallons as a safety margin, not included in the Distance To Empty estimate / forecast. The Forester does not, leaving no safety margin in this estimate whatsoever. (It also rounds DTE to the nearest 10 miles.) But it does have 3 other advance warnings at different stages, so drivers do get plenty of warning before fuel starvation.

    The Prius display reduces or hides some of the variations plainly visible in the Forester, but the underlying forecasting difficulties are the same.
     
    #308 fuzzy1, Feb 18, 2019
    Last edited: Feb 18, 2019
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  9. Mendel Leisk

    Mendel Leisk Witness Leader

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    I never pay any attention to that DTE info. I keep an eye on the gas gauge.
     
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  10. fuzzy1

    fuzzy1 Senior Member

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    This is clearly the easiest way to avoid overthinking this uncertain forecasting guesstimate.
     
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  11. sam spade 2

    sam spade 2 Senior Member

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    That's good but you should have at least a rough idea of the full tank range in the back of your mind and reset the trip ODO on each fill.
    That way, if someday you get this little feeling that the gauge is lying to you, you have something to check it against.

    I'm a bit more sensitive to this than most.......having ridden motorcycles for a LONG time with NO gas gauge at all.
     
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  12. Mendel Leisk

    Mendel Leisk Witness Leader

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    Yeah I reset trip meter too.
     
  13. alanclarkeau

    alanclarkeau Senior Member

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    Did you fill the tank up completely? And how many tanks - is this your first tank. The "Distance to Empy" will ONLY work if the tank is completely filled (to first click). Then drive at least a few hundred kilometers.

    Some trips my car will use 5.5l/100k, other days just 3.6. It depends on many factors - traffic density, your mood, how full the battery was at the start (and at the end), how many times you're forced to stop, temperature.

    Driving with economy in mind helps too. If I'm in a real hurry, I can use 30-50% more fuel by pushing it harder - BUT - that's the same with any car.

    Don't overthink it - just drive. Always completely fill your tank. Record EVERY fill. You can't work out how much you're using by individual trips.