Fill Up when Tank is Empty, Quarter Full or Half Full?

Discussion in 'Gen 4 Prius Fuel Economy' started by Marshmallow, Jul 20, 2016.

?
  1. When I'm On Empty

  2. When I'm 1/4 Tank Full

  3. When I'm 1/2 Tank Full

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  1. Mendel Leisk

    Mendel Leisk Witness Leader

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    I'm pretty sure there's no separate tank emergency reserve, it's all one tank. And when it's low a sharp corner or sudden braking, basically anything that'll slosh the remaining gas, could lead to momentary air in the line.

    I did have emergency reserve on me first bike, come to think of it. When the engine started to stumble you reached down and flipped a toggle, and seriously started looking for gas.
     
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  2. krmcg

    krmcg Lowered Blizzard Pearl Beauty

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    Me too. What a sinking feeling when you reached down and realized you never reset the lever...
     
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  3. bisco

    bisco cookie crumbler

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    it is one tank, but it's still emergency reserve, and i don't know what kind of wild driving you'd have to do to slosh it around enough to get air in the line, if there's even air in there.
     
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  4. alanclarkeau

    alanclarkeau Senior Member

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    The failed fuel pump was on a VOLVO 240 - probably exacerbated by sucking up sludge in the bottom of the tank. I put 2 gallons of fuel in the tank and it wouldn't pump - all the fuel lines and pump were cleaned out, but in the end I needed a new pump. There were problems with some early Fuel Injection systems (mid '80s Nissan for one) which needed bleeding if they ran out of fuel - but I think that's long past.
     
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  5. ETP

    ETP 2021 Prime(Limit),24 Venza Limit,B52-D,G,F,H

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    Like scuba diving and you reach for the reserve lever and it is already pulled and your are two miles of the coast of Guam.:mad::cry:
     
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  6. krmcg

    krmcg Lowered Blizzard Pearl Beauty

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    Exactly.
     
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  7. fuzzy1

    fuzzy1 Senior Member

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    I usually lean more toward MP$. MPG is a simplified proxy for that.

    Knowing a more accurate MPT than the vague swag of common fuel gauges enables greater capacity for taking advantage of fuel pricing differences. Think of it as a form of price arbitrage. Not everyone is cut out for the math and planning necessary for this.
     
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  8. cproaudio

    cproaudio Speedlock Overrider

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    I'm a risk taker. I took a 330 mile trip with DTE indicating 306 with 2 other person. On return trip, the last pip started flashing at 63 miles away from home. Sure there were gas stations on route but since they're in the middle of nowhere, they were price gouging. I risked it and drove straight home. My point is that just because the DTE has reached 0 doesn't mean your car is going to stop dead 1 mile pass the 0 DTE mark. the Prius has about 2 gallons of gas left when the low fuel starts to flash. You are safe to drive at least another 50 miles before you hunt down a Shell station. I'm pretty sure the 2016 Prius is the same. In fact, I'm pretty sure all the recent Toyotas are like that.
     
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  9. ETP

    ETP 2021 Prime(Limit),24 Venza Limit,B52-D,G,F,H

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    This thread is kind of like, "should you argue with a policeman with a gun or say yes sir yes sir 3 bags full?" Or I have a gun let me get it for you:ROFLMAO::LOL:
    IQ test BTW.

    I put my hands on top of the steering wheel and do what I am told and nothing more or less.

    Fill up often, live long and prosper.
     
  10. Marshmallow

    Marshmallow Junior Member

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    not to sound like a douche or anything, cause i'm so new here, but...

    if that's that case, than why do people keep comparing how many miles they can get per tank? it's not like we're adding inches to our penis' by getting more miles per tank than the next person, so why do people do this?

    don't get me wrong, i hit 645 miles on my first tank, and i'd love to hit over 800, but like you said, mpg matters, not mpt.

    i guess the thing is, you know that screen where you input how much gas cost per gallon after you fill up? what happens when you got half a tank, and decide to go get gas from somewhere, and it ends up costing more than the previous place?

    i got gas where it was around $2.65 per gallon, what if the next spot i go to is $2.80 per gallon? does the computer average out between the half tank that still has gas that was $2.65 and the other half that cost $2.80, or does it calculate the distance you drive by the $2.80 per gallon?

    am i making sense, or am i rambling? if i need to post photos to get my point across, i will.
     
  11. bwilson4web

    bwilson4web BMW i3 and Model 3

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    Absolutely correct:
    I had used MPG when comparing like energy sources. But when I added a REx, I adopted $0.0x/mile for EV operation because it is money out of my pocket. The irony is our Huntsville utility rate, $0.10/kWh, is relatively low like our history in gasoline prices, $1.88/gal regular today. Still, I can also do the REx calculations too:
    • $0.036/mile - Gen-3 Prius, @65 mph, 52 MPG, $1.88/gal
    • $0.054/mile - BMW i3-REx, @65 mph (50 mph block-to-block), 40 MPG, $2.15/gal (premium)
    So my benchmark is Huntsville-to-Nashville, 120 miles, gas-only:
    • $4.32 - Gen-3 Prius
    • $6.48 - BMW i3-REx
    Compared to the Gen-3 Prius, the BMW i3-REx is not a great, cross-country car. But it can reliably make the trip. Actually, we can split it 50-50 electric and gas:
    • $1.62 - EV 60 mi, $0.027/mile, 65 mph
    • $3.24 - BMW i3-REx, 60 mi, $0.054/mile, 65 mph without refueling
    • $4.86 - total cost
    Bob Wilson
    Merged
    Because filling a tank is an overhead function that steals time from our lives and dollars from our wallets.

    Bob Wilson
     
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  12. tpenny67

    tpenny67 Active Member

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    I agree that there's no separate reserve, but "empty" (when the last PIP is flashing) is a bit conservative thus giving some extra "reserve". In my mind, this is the car trying to get the driver to fill up *now*, and also allowing for the case that the first gas station is a few miles away and may be closed/out of gas/etc requiring additional driving to get to the next station.

    BTW, my understanding is most gas tanks have internal baffles or some other means of holding some fuel close to the fuel pickup. This isn't just for the momentary slosh, but also for prolonged cornering on an entrance ramp, stopping on a steep driveway, etc.
     
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  13. ETP

    ETP 2021 Prime(Limit),24 Venza Limit,B52-D,G,F,H

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    Yes = fill up now. BTW the computer should say "why did you wait so long"? I stop to go to the bathroom, get something to eat, fill up, check my tires, check my earl, stretch my legs, and clean my windshield. :ROFLMAO::LOL:

    This time is well spent for bonding with your car as well as a safety issue folks. Filling up every 500 miles is not a big issue. More like 300 for me as I have a small bladder.

    Probably more important items to test than lets see if I run out of gas.
     
  14. RRxing

    RRxing Senior Member

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    I do not know the correct answer to this - bragging rights???

    All I know is (potentially) allowing your tank to run dry and leaving you stranded, or worse, damaging your car, for whatever reason, is a fool's errand.

    As far as keeping costs low, I keep a spreadsheet that's updated every fill up, and allow dollar cost averaging to take care of the rest. Getting more than twice the MPG than most non-hybrid cars is more than enough savings for me, so it makes little to no sense in trying to save less than a quarter per fill up by waiting/searching for the cheapest gas.
     
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  15. krmcg

    krmcg Lowered Blizzard Pearl Beauty

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    I called it!
     
  16. ETC(SS)

    ETC(SS) The OTHER One Percenter.....

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    Asked and answered.

    I have no problem with people trying to break 800 miles per tank in their cars, and if you think about it, it's a fairly conclusive acid test for real-world efficiency versus some of the shenanigans that people engage in just to game the system and get a "high score" on their MDF.

    If you're going to suggest that running a car out of gas can damage it, then I'm going to need a more convincing argument than the old "fuel pump" myth, which at least is slightly more plausible than the even older "crud at the bottom of the tank" story from a few decades ago.
    The one real concern is damage to the evaporation containment system from over-filling, but that's not been a problem for my G3 since I tend to cease fueling after the pump clicks off.
    Of course, since I live in a place where a VET is some place to take a sick pet, and since "my" Prius is company owned I don't really sweat the Evap system anyway.... ;)

    I guess the main point is that I let people drive their cars the way that THEY want to.
    If somebody wants to break into the 900-mile club? (VERY possible with the G4!)

    More power to them!
     
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  17. booke02

    booke02 Active Member

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    A man after my own heart! I do exactly the same thing.
     
  18. krmcg

    krmcg Lowered Blizzard Pearl Beauty

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    Don't we all?
     
  19. Mendel Leisk

    Mendel Leisk Witness Leader

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    Are the later cars (3rd and 4th gen) still willing to run the hybrid battery down to the point it takes special chargers to (hopefully) revive them, in the event of an out-of-gas electric-only roll to gas station? I'm not sure.
     
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  20. tpenny67

    tpenny67 Active Member

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    I've also heard of Porshes that need to be towed after running out of gas to reset the computer. Apparently the computer sees the engine stumbling as a serious mechanical problem and blocks restarting of the car to prevent damage.

    I've seen a lot of auto makers brag how they durability test their cars but so far nobody has mentioned a "run out of gas 100 times" type of test.