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Fuel saving technique at gas station

Discussion in 'Prius c Main Forum' started by mdgates, Jun 2, 2014.

  1. mdgates

    mdgates Junior Member

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    As I pulled up to the gas station today, I had a thought. You must not fuel a vehicle with the engine running, but what about a Prius with the engine off, the gear selector in N, and the car "on"?

    Normally, I pull the keys at the gas station, and the stupid Prius goes into S1 and kills my fuel economy for the rest of the drive home. This time, I left the car on (engine off, N), fueled while I watched the fuel gauge on the dash jump from one bar to five bars to ten, then drove off still in S5. The car didn't complain whatsoever, and it didn't ask me about what the price of gas is today. Very nice.

    Of course, I don't guarantee you won't burn your car down if you try this, even though I can't think of any plausible mechanism that could ignite fuel vapor only in this scenario.
     
  2. Mendel Leisk

    Mendel Leisk EGR Fanatic

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    The car could start running the engine while you're refuelling. That's not good.

    Also, maybe it's a prius c term, but I have no idea what S1 is, even less regarding S5. I can't see your fuel economy plunging 'cause you turned the car off for a few minutes.
     
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  3. mdgates

    mdgates Junior Member

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    The engine can't start while the car is in "N".

    S1-S5 refer to the stages of prius warmup: The Five Stages of Prius Hybrid Operation | PriusChat

    If you turn the car off and back on, you'll find it starts drawing heavily on the battery and keeping ICE RPMs low. Basically a golf cart, plus idling the engine. After about 30s of that, it switches to battery-charging mode, and you'll see ~20-30A entering the battery for a minute or so. During this time, you can't get into EV mode. Since I live three minutes of city driving from the gas station, I feel really dumb idling the engine to whole way home.
     
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  4. NR427

    NR427 Member

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    I might try this. I only live 4 blocks from my gas station plus it's downhill to my house. Anything above 2 bars of battery and I should be able to get home on EV.
     
  5. Mendel Leisk

    Mendel Leisk EGR Fanatic

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    Leaving it in Neutral serves no useful purpose I can see, too. Sorry, can't see this "killing your fuel economy".
     
  6. 2k1Toaster

    2k1Toaster Brand New Prius Batteries

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    I generally fill my GenII with it READY. But I put the car in EV mode and the engine will not turn on. This is illegal in my area though because the vehicle must be off, not just the engine.

    It does save gas because it prevents another warmup. It is very minimal and risky if you are not careful.
     
  7. mdgates

    mdgates Junior Member

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    Very incorrect. There are several subtle techniques relating to leaving it in N, which are documented on these forums. N prevents certain behaviors including electric flow to and from the battery (and therefore engine starting), which have niche fuel saving applications.
     
  8. Spock

    Spock Junior Member

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    it's 3 minutes of driving...i think you're obsessing a bit too much with the MPG counter - I know, I've been there! I hate to see something like "35mpg for your trip" no matter what the length is. But really if my trip is like, .3 miles or so I realize in the grand scheme of the cosmos that is not THAT much gas used. :cool:
     
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  9. JimN

    JimN Let the games begin!

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    mdgates, been doing this for years but the car is in park. I turn off everything that draws current. The only reasons the ICE will spin up are if the SOC is too low or coolant temp is too low. This could happen if you live above the gas station or the gas station is located in your residential neighborhood. In extreme cold engines are never turned off.

    I'll just park & lock the car for short trips, say 5 or 10 minutes. Every little bit helps.
     
  10. HotDogWater

    HotDogWater Junior Member

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    If it's just a quick fill up, I usually hit the EV mode button before the engine starts running and it's fine until I get to 25mph.
     
  11. Paul Schenck

    Paul Schenck Active Member

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    I just tell the gas station attendant it is off, it runs on battery. put it in park emergency break on. Or I push the voice command button and say " Screen off " but then I'll also leave it running on a hot day and take the key into a store.


    iPhone ?
     
  12. wjtracy

    wjtracy Senior Member

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    Well I get the MPG point...in fact sometimes it seems like MPG never comes back to where it was before the gasoline stop.
    But (re: gaso fill-up) unless the owners manual or Toyota says this is a valid approach, which I presume it says turn off car, it is not safe in my book. True that most of rare issues at the pump have to do with static electricity build-up, but there are some other possible scenarios like someone hitting your car at the pump or someone spilling a bunch of fuel on the ground.

    I mean we can check out Chevron web site for re-fill safety guidelines, and Prii/Volt/Ford Fusion owners manual, various other safety and industry orgs, I think we probably know what they say.
     
    #12 wjtracy, Jun 5, 2014
    Last edited: Jun 6, 2014
  13. Your hybrid is still using battery power while the car is "on" and won't like if the charge gets too low.

    Mine does if my battery's charge drops below halfway and/or the engine temperature gets low.


    And besides it isn't saving gas because you use gas later to recharge the battery (the energy that you used while keeping it "on" in the first place). Why not just turn the car completely off?
     
  14. ztanos

    ztanos All-around Geek!

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    It will throw a PO442 Code. Minor evap leak. This is due to air getting in through the unsealed system. You will either have to clear the code, or do a few cycles.

    Note: This can also pop up due to a bad gas cap seal.
     
    #14 ztanos, Jul 2, 2014
    Last edited by a moderator: Jul 3, 2014
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  15. Ashlem

    Ashlem Senior Member

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    I live close enough to a local gas station, about four city blocks, that I usually just gas up after coming home from work, which is about a 30 minute drive. I just turn it off, gas up, then put it in EV mode after turning it back on, and then just drive really slow back home, which takes about a minute and a half or so.

    It also helps that there's a semi-private lane I can turn into which is off of the main road, so I don't have to worry about holding up traffic. It's also mostly on a slight downhill path, so I can essentially glide the entire way home.

    I don't think I would want to leave the car on just because it might cause a bad habit to form, and I forget to turn it off later. Plus I don't like hearing the c whine whenever I leave the car on and exit it with the fob in my pocket. And I'm certainly not leaving the keys in the car, only to have someone steal and drive my car away (this happened to my brother at his pizza delivery job a few years back when he left his car running to grab some pizzas to deliver, only for a car thief to then drive off with it. Thankfully we found it the next day a few blocks away, and he used the spare key to drive it back home).
     
  16. ETC(SS)

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

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    I used to think that states like Oregon and New Joisey were moronic for mandating that customers not pump their own fuel, but now I'm not quite so sure.

    I do not know.
    I'm thinking that it's just easier just to turn the car off when you get gas.
    Neutral?
    Yeah. The car won't start, and you're probably going to remember to apply the parking brake....and release it when you're done.
    Maybe the car being booted up won't cause any issues......but really?

    I'll just do it my way...thanks.

    Good Luck.
    :eek:
     
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  17. engerysaver

    engerysaver Real Senior Member

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    I don't have a Prius c; but this is what I would do:
    On a HOT day, with many bars slowing, I'll cut off the A/C, I put my Prius in park; sometimes I set the brake, Prius is still in the READY mode, I get out and pump my gas; when finished, I get back in and go way way.:)
    The Prius drives, just like I don't stop at all:cool: ..... NO changes at all!!(y)

    If you cut the Prius off .... when you turn the Prius back on; the Prius has to go through its checks and warm-up stages, with ICE running; which makes for poor MPG:(!!
     
  18. RichJabo

    RichJabo Junior Member

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    How long does it take you to fill up your car? I use a gas station about 4 city blocks from my home. If I stop for gas on the way home I shut off the engine. After filling the engine is still "warmed up" enough to drive home without engaging the ICE and without putting it in EV mode.
     
  19. ztanos

    ztanos All-around Geek!

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    I don't see any benefits in this... sitting in EV mode is still letting the engine cool off, just like if you actually turned the car off. The only thing that I could see even being close to beneficial is the MPG gauge for the trip... but there are too many negative reasons not to do it. But YMMV and to each their own.
     
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  20. Mendel Leisk

    Mendel Leisk EGR Fanatic

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    I'm thinking the OP has an idea that when you shut the car off completely, it's resetting something in the software, and at restart, the next mile or two will have compromised fuel efficiency, again just due to the software, having to go through some steps, to get back to optimum efficiency?

    But, I still don't get it, don't follow the logic to begin with, and think the dangers (hell, the illegality) trumps any gains.