Will the Prius Prime use gas even if in EV mode?

Discussion in 'Prime Main Forum (2017-2022)' started by charliebrownsprius, Nov 17, 2020.

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  1. charliebrownsprius

    charliebrownsprius New Member

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    I've had my Prius Prime Hybrid plugin for about 1 month now and noticed that in these 30 days, I've used about 1/4 tank of gas.

    All of my travel has been on electric.

    I'm just wondering what would have accounted for a 1/4 tank of gas being used? I was hoping to eliminate all gas used because all of my daily trips are on EV.

    Thank you
     
    #1 charliebrownsprius, Nov 17, 2020
  2. schja01

    schja01 Senior Member

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    There is a max speed for EV mode.
    If temp is below 16°F and heater is used
    If defroster is used.
    Just to name a few
     
    #2 schja01, Nov 17, 2020
  3. charliebrownsprius

    charliebrownsprius New Member

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    Would you happen to know what is the max speed before EV stops working? All of my driving is within the city so my max speed is perhaps 60 km/h (roughly 37 miles/hour)
     
    #3 charliebrownsprius, Nov 17, 2020
  4. mr88cet

    mr88cet Senior Member

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    84MPH.
     
    #4 mr88cet, Nov 17, 2020
  5. john1701a

    john1701a Prius Guru

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    135 km/h (84 mph)
     
    #5 john1701a, Nov 17, 2020
  6. Gokhan

    Gokhan Senior Member

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    Turn on the eco gauge on the multifunction display. In the EV mode, the EV icon is green and when the ICE kicks in, it's grayed out; so, it's hard to miss the ICE running. It also displays the battery percentage.

    [​IMG]
     
    #6 Gokhan, Nov 17, 2020
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  7. sam spade 2

    sam spade 2 Senior Member

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    P.S. You really can't completely avoid using any gas at all because..........if you do, the gas in the tank will go "stale" and gum up the works.
    I think the Prime will automatically force you to use some gas every 6 months or so.
     
    #7 sam spade 2, Nov 17, 2020
  8. mr88cet

    mr88cet Senior Member

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    I generally take mine to the gas station once every 2-3 months, and put in 2-3 gallons each time.
     
    #8 mr88cet, Nov 17, 2020
  9. fuzzy1

    fuzzy1 Senior Member

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    I'm not sure why anyone keeps asserting this, in the face of so many Prime owners saying otherwise.
     
    #9 fuzzy1, Nov 17, 2020
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  10. sam spade 2

    sam spade 2 Senior Member

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    OK, so what really IS the truth ?
    Is it another model that does that ?
    Or does it just pop up a reminder warning that you need to use some gas ?

    Or are you saying that it does NOTHING and will just let you keep the same gas in the tank until it is 5 years old without any warning ??

    So straighten me out please.
    I will try to remember the answer.
     
    #10 sam spade 2, Nov 17, 2020
  11. charliebrownsprius

    charliebrownsprius New Member

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    Coincidentally, I did set this up the other day. I see the green EV symbol and have noticed that the times I am with my wife and she has the heat up and the defrost running, the green symbol does grey out.

    I'm just surprised that her using the amenities of the car (heat/defrost) would impact the gas. I did read a few posts that it would impact the electrical charge which makes sense, but gas as well?
     
    #11 charliebrownsprius, Nov 17, 2020
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  12. charliebrownsprius

    charliebrownsprius New Member

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    This seems to match up with my experience.

    I thought I read the Prius has roughly a 40 liter tank and I've used about1/8th of a tank or 5 liters. That's about 1 gallon of gas in one month.
     
    #12 charliebrownsprius, Nov 17, 2020
  13. mr88cet

    mr88cet Senior Member

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    My understanding from multiple sources is that the Volt does/did so, but personally don’t know either way in the case of the Prius Prime. I have never kept enough gas in the tank to find out.
     
    #13 mr88cet, Nov 17, 2020
  14. mr88cet

    mr88cet Senior Member

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    Perhaps the only difference then is just simply noticing when its running. It’s pretty quiet, usually. The hybrid-usage display helps with that.
     
    #14 mr88cet, Nov 17, 2020
  15. t_newt

    t_newt Active Member

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    From an older post from Lee Jay about the windshield defrost:
    It pumps heat from the ICE coolant through the air conditioner evaporator coil with the AC running to dehumidify that air. That means the heat and the air conditioning are on at the same time.

    It can't use the heat pump for the front defrost because it is using it for air conditioning, so it has to turn on the engine.
     
    #15 t_newt, Nov 17, 2020
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  16. Salamander_King

    Salamander_King Senior Member

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    If all of your travels have been really EV mode only and you did not cause the engine to come on, then your Eco diary log would show the maximal mpg 999.9mpg for the last 30 days. Anything less than 999.9mpg, you used some gasoline for that day. This is also true for the ODO corresponding or even Trip Meter corresponding mpg on the dash. If the car was never driven on the engine using gas, it will show 999.9mpg. However, chances are that the car was driven some miles with the engine using gas prior to you purchasing the car, so the dash mpg indicator is most likely to be less than 999.9mpg.

    Since you are in Canada, the unit is set different IIRC. I am not sure what 999.9mpg is in Canadian units. @Tideland Prius may able to help me here.

    If indeed, you have had 999.9mpg for the last 30 days on the Eco Diary log, then your gas gauge is off. Maybe it was not full tank at the dealer?
     
    #16 Salamander_King, Nov 17, 2020
    Last edited: Nov 17, 2020
  17. john1701a

    john1701a Prius Guru

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    Electric heating is effective most of the time for removal of condensation from the windshield. So, just using that option on the screen is a good first step. Most of the time here in Minnesota, that's all I need.

    Pressing that dedicated "defrost" button will fire up the gas engine, since you are instructing the system to also dehumidify. The purpose of the heat-pump will then change to the role of A/C and warming will come from the heated coolant.

    Think of the button as MAX defrost. It's there for your convenience, but often not necessary.
     
    #17 john1701a, Nov 17, 2020
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  18. Tideland Prius

    Tideland Prius Moderator of the North
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    The engine comes on quite smoothly so it's possible it came on without you knowing.

    Some scenarios for this time of year include

    • Heating (requesting more heat than the heat pump can provide)
    • Turning on the front defroster by pressing the front defroster button to the left of the screen (11.6" MFD) or in the climate control area (7" screen)
    Once the engine is running, it will go through its warm-up cycle.

    That said, 1/4 of a tank seems like a lot. I've only gone through 3/8ths since March and I've deliberately used gas on occasion (like in June, I drove 30-40 km on the highway in hybrid mode to let the engine run up to operating temp at least once this calendar year).

    Yes and no. For my daily drive, I absolutely can avoid driving in HV mode (free charging around the city helps keep me in EV mode).

    I don't think we've confirmed that 6 month period. Most people would've gone into HV mode just because they ran out of charge or live in a place where it gets colder than -10°C. I could try if you really wanted to. Last year, my record was 72 or 76 days (whatever I wrote in that thread) and only because I was going on a road trip, that my experiment had to end.

    It pops up a reminder. It says so in the owner's manual. To avoid that pop up reminder, you must refuel at least 20 litres (doesn't have to be all in one go apparently, according to the manual) in a 12 month period.

    The tank is 43 litres. The low fuel light comes on after 35 litres have been consumed.

    If nothing was used, 0.0L/100km will show. Now you can still use gas and get 0.0L/100km if your daily travel in EV was long enough (and the engine run time was short enough) that the average is less than whatever the computer's threshold is for rounding down to 0.0L/100km instead of rounding up to 0.1L/100km.

    I know that because the engine did come on in August but yet that monthly record is 0.0L/100km and the day I ran it, I was in EV for the majority of the day so the average was rounded down to 0.0L/100km.
     
    #18 Tideland Prius, Nov 17, 2020
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  19. charliebrownsprius

    charliebrownsprius New Member

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    I wouldn't be able to comment on what happened at the dealership, they may have driven it on gas but it would have been minimal because it was a new car and when we picked it up, they were literally removing the clear wrapping around the seats.

    Once we took it off the lot, we went to a gas station and filled the tank so that this would be our benchmark.

    Since then, all of our trips have been under 40km. I'll check the diary when I get home to see what it says.
     
    #19 charliebrownsprius, Nov 17, 2020
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  20. Tideland Prius

    Tideland Prius Moderator of the North
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    Also driving in B and going down a hill can kick the engine on (even in the summer). If your speed increases, that means the regen isn't strong enough and the car thinks that's a safety issue so it'll kick the engine on to provide the actual engine brake and once the engine is on, it'll run its warm up cycle.
     
    #20 Tideland Prius, Nov 17, 2020
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