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Is Your 'Remaining Fuel' Indication Off?

Discussion in 'Gen 1 Prius Plug-in 2012-2015' started by radiocycle, Apr 25, 2012.

  1. radiocycle

    radiocycle Active Member

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    We just filled the tank for the first time, since coming from the dealer. I got a little bit nervous because the remaining fuel indication said I had 5 miles left and I was about 12 miles from home. But, I found a station and pulled in for a fill-up. It took 8.802 gallons! I think it's a 10.5 gallon tank, so what's up with the indication being so far off? Will it some how calibrate the instruments over time?

    r
     
  2. jbrad4

    jbrad4 Active Member

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    Because the gas in the tank cools the fuel pump, you don't want to make a habit of running the tank almost dry. With the fuel pump located in the tank, they have to drop the tank to replace the fuel pump. I make a habit of never going much below a quarter tank before I fill up.
     
  3. wmmmmm

    wmmmmm Junior Member

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    I was wondering the same thing. On my first fill-up, I waited until there were no bars remaining and I filled 8+ gallons (I forgot how much since I'm not in the car). I didn't notice any low fuel indicator but maybe I just didn't notice it. But as I am approaching my 2nd tank, there's still two bars left but the range to fill-up shows only 40 miles. I would think with 40 miles left (that's less than a gallon), the car would turn on the low fuel indicator. As for your indicator saying there's 5 miles left, it makes me laugh because according to my math, that's about two ketchup bag's worth of gas! I can imagine the fuel pickup sucking up literally the last drop of gas to get that 5 miles!
     
  4. wmmmmm

    wmmmmm Junior Member

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    There are many reasons a gas tank shouldn't run near empty and I also fill up soon after the gauge drops below a quarter tank. But as part of my new car ritual, I try to run it as empty as I can just so I am "calibrated" with the fuel gauge. The PIP is making it difficult:D
     
  5. radiocycle

    radiocycle Active Member

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    Yes, your point is well taken. And our 2010 had a 'built-in fudge factor' so that even when down to last blinking pip and the instrumentation indicated that there were only a few miles left before empty, there was still a small quantity of fuel left in the tank; enough to find the nearest station anyway. But almost two gallons seemed a bit much to me... How 'bout accurate gauges and then leave it to me to use the information to the best advantage??
     
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  6. fuzzy1

    fuzzy1 Senior Member

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    Fuel gauging 'error' and 'inaccuracy' is probably one of the top ten subjects of new threads in PC. I too would like an accurate gauge. But short term fuel consumption is very highly variable, due to changes is weather, road conditions, elevation change, engine warmup for short trips, driver style, and numerous other factors. Driving range estimates will always be subject to significant errors.

    On top of these, most drivers have poor knowledge of these factors, poor math ability to make their own adjustments, poor planning, and poor attentiveness to the gauge. An 'accurate' gauge will be wrong in one direction half the time, and in the other direction the other half. The human factors problem will then cause numerous people to run out of gas. Many of them will be complain to Customer Support, sometimes very furiously, about the 'defective' gas gauge causing them be be stranded. Some will also go on to automotive web sites and complain very bitterly about the 'defect'.

    Customer Support is already a very nasty job without this unnecessary flood of PO'd customers. It is much better to build in a couple gallons of safety margin.
     
  7. ClaySacramento

    ClaySacramento Junior Member

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    I was paying attention to the cruising range indicator in relation to the fuel meter/bars last week and found that the final bar on the fuel meter started flashing (low fuel level warning light) when I had 5 miles of cruising range remaining, but I also had about 5 miles of EV range at the time.

    According to the owner's manual, the low fuel level warning light comes on when "remaining fuel is approximately 1.6 gal. (6.0 L, 1.3 Imp.gal.) or less". When I refilled shortly after the low fuel level warning came on, I was able to fill 8.67 gallons, so I should have had just under 2 gallons remaining in the 10.6 gallon tank.

    I searched through the owner's manual for warnings about letting the fuel run too low (since the manual seems to contain plenty of warnings for everything else) and the closest I found was "Check the fuel amount and refill immediately when the fuel level becomes low." (on page 40). I didn't see any warnings/recommendations to refill the tank before the low fuel warning light comes on.

    Regarding running out of fuel, the owner's guide states, "When the vehicle has run out of fuel and the hybrid system cannot be started, refuel the vehicle with at least enough gasoline to make the low fuel level warning light (␣P. 537) go off. If there is only a small amount of fuel, the hybrid system may not be able to start. (The minimum amount of fuel to add to make the low fuel level warning light go out is about 1.9 gal. [7.1 L, 1.6 Imp.gal.], when the vehicle is on a level surface. This value may vary when the vehicle is on a slope.)"

    The fuel-related warning that I found repeated the most (four times) throughout the owner's manual was to "Refuel at least 5.3 gal.(20 L, 4.4 lmp.gal.) of fuel every 6 months".
     
  8. bisco

    bisco cookie crumbler

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    to keep it from getting stale and excercising all the ice related parts for people who are driving almost exclusively electric.
     
  9. iRun26.2

    iRun26.2 New Member

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    Has anyone ran out of gas yet?

    Has anyone seen the 'low fuel warning light'?
     
  10. wmmmmm

    wmmmmm Junior Member

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    Okay. I saw it today also. With 23 miles left, the dash made a ding noise and the last one bar starts to flash. I drove it down to 9 miles left (with10.5 ev miles) before putting in 9.05 gallons. That's the lowest I'll go. Done.
     
  11. devprius

    devprius /dev/geek

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    The behavior of the low fuel warning is pretty consistent with every Toyota I have owned in the past 16 years: low fuel light comes on (or flashes on the MFD/MID) and I have 2 to 3 gallons of fuel left in the tank. When the low fuel warning comes on and the last bar starts flashing, I will try to get gas within the next 20 or 30 miles. In the case of the PiP, it will usually take between 8.5 and 9 gallons at that point. That still leaves an estimated 1.5 to 2 gallons in the tank. I find that the DTE is a very rough indicator of when the last bar on the gas gauge will start blinking, not when I'll actually run out of gas.

    Toyota, as well as other manufacturers, have tough line to walk here. On one hand, we consumers want an accurate gas gauge so we can better gauge exactly how far we can go on a tank. This is especially important when we're on the open highway where gas stations might be few and far between. But we also want a fair amount of warning before we do run out so we can find gas before that happens. And the reality of driving is that gas usage over a particular amount of miles can vary a huge amount depending upon traffic, hills, A/C usage, etc. To deal with this dilema, and avoid angry complaints from people who have run out of gas, Toyota seems to have adopted a 2-prong approach to this problem. They give us a DTE estimate that is on the conservative side and they also try to warn us well ahead of time that maybe it's time to get gas.

    It is a little annoying to have the low fuel warning light come on, go get gas, and then find out that you still had 2 gallons of gas left. But it's way more annoying to run out of gas because you decided to push things. Don't ask me how I know this...
     
  12. fuzzy1

    fuzzy1 Senior Member

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    In my experience, the same is generally true of Ford, Honda, and Subaru going back twice that age.
    The very first car I actually owned, a bit older than my timeframe listed above, had a gas gauge almost perfectly accurate, much closer to actual fuel level than any car since. (Not sure how it came from the factory. It could have been shifted by original owner's accident damage & repair.)

    Keyword: Almost. On my very first tank, it ran dry with the needle slightly above E. This is the short ranged car that later made me acutely aware of the lack of fuel availability on certain routes outside of standard business hours.

    My next Ford was tested by intentionally running it dry, Bob Wilson experiment style, in benign conditions. It went over a hundred miles past the warning, making me comfortable with going forty miles over on a somewhat common basis. I've never performed this experiment on a fuel injected car.
     
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