Fuel consumption at cold during first phases

Discussion in 'Gen 4 Prius Fuel Economy' started by Furina, Feb 10, 2018.

  1. Furina

    Furina New Member

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    Hello,

    What is your fuel consumption during the early cold phases?

    I feel that mine consumes a lot.
    Temperature of 40F.

    During S1 phases it runs at 1500 RPM. S2 1300 if I leave the heating.
    Always it is that in 3 minutes of these phases it consumed 150 ml (0,039 gals). That's 3L per hour (0.79 gals).

    Note that during the first phase, the engine knock a little but my dealership didn't find anything... I read on this forum that there is an overconsumption at startup. But as much?

    Consumption decreases quickly as soon as my engine is hot. My consumption is currently 5.7 L / 100 (41mpg) on long trips

    The problem is that on short trips, the high consumption of the beginning make the average very high. Below a 10km (6.2 miles) trip, I have a consumption that exceeds 8L / 100 (33mpg). It takes more than 16 km for me to get below 6L / 100.

    What do you think ? And if it's abnormal where it can come from?

    My car have 25000km , 1 year. 17 inches tires.

    Thanks
     
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  2. ForestBeekeeper

    ForestBeekeeper Active Member

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    You are seeing this at 40F?

    We see decreased fuel economy at -20F for certain.
     
  3. bisco

    bisco cookie crumbler

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    welcome!
    .78 gallons in 3 minutes?:eek: edit: sorry, read that wrong. one hour? that sounds reasonable.

    sorry to say, but consumption sounds about right. short trips are a killer, but much worse in a gasser.
     
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  4. grid

    grid Member

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    40 f or below, takes 3.5 minutes for ice to stop when starting engine from cold soak. Avg mpg loss around 5 every cold mornings :(
     
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  5. 4est

    4est Junior Member

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    It seems normal
     
  6. Furina

    Furina New Member

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    Ok, you reassure me. Every day I make trips of about 17km (10 miles) . At 62F, I was 5.4L / 100 (43MPG) in the morning, 4.8 L / 100 (48MPG) at evening.

    But now it is colder. Morning at 40F. Can't do less than 7L/100 (33MPG) on this work trip :(.
     
  7. bisco

    bisco cookie crumbler

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    leave a little earlier, and take the scenic route. it will use more petrol, but your mpg's will go up.(y)
     
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  8. pilotgrrl

    pilotgrrl Senior Member

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    Your stress level will decrease, too.

    I find that true, especially since the mothership moved to Plano, where the traffic's gotten a little insane.
     
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  9. alanclarkeau

    alanclarkeau Senior Member

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    Yes, cold affects it. If you turn your Climate Control OFF, it may not start the ICE - otherwise it's trying to warm not just the engine, but you too.

    The warm up process takes a short-term hit on economy. It's summer here - our temps are about 30-35 C max at the moment (I think that's in the 90s F). The first 12-15km of a trip seems to not be as good as distance beyond that.

    A typical 21km trip I take:
    • I start off from home, my first 1km show 0l/100 (zero) - as it's a bit tortuous and can't really get any speed up and it stays in EV - at this stage, battery shows only 2 bars;
    • The ICE starts, then after 4km as I pull onto the Motorway it is showing 6½-7l/100km;
    • 10km along Motorway (total trip now 15km) it shows 4.8-5.0l/100;
    • another 5km along Motorway and 1km through back street - at the end of my journey (total trip now 21km) it shows 3.8l/100km.
    Return journey - similar.
     
  10. Furina

    Furina New Member

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    On my side, unfortunately (in winter) can't do better than 5.5L/100.
     
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  11. kithmo

    kithmo Couch Potato

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    Sorry to un-reassure you but by 10 miles you should be up near 60 mpg(UK) easily. I do lots of short trips and before I retired last year my commute to work was only 3.5 miles each way and the worst I got in winter was around 43 mpg on the trip computer.
    As I'm pootling about nowadays a round trip of say 7 or 8 miles (at 40F) will get me up in the high 50s or more. Once the engine is warmed up enough I'll go to mid 60s, this is with the heater on.
     
  12. Furina

    Furina New Member

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    If I consume too much what can it be? I calculated my BSFC using the torque software which is 344. But I do not know how to interpret it or if it's bad.

    Tonight he was 49F. At 70 mph: 47 MPG (UK). Stable : 24 miles trip.
    56 MPG average for the trip, thanks to a few km at low speed in EV mode.

    Its ok?
     
  13. bisco

    bisco cookie crumbler

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    is okay.
     
  14. kithmo

    kithmo Couch Potato

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    47 mpg UK is only 38 mpg US, 56 mpg UK is 45 mpg US, I would say that's low for a Gen 4, on a 24 mile trip.
     
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  15. Furina

    Furina New Member

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    Car dealer find nothing wrong... And assures me that my consumption is normal ... Even if I realize that you do better! I may have fallen on the wrong model of prius.
     
  16. bisco

    bisco cookie crumbler

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    you can't compare your stats with another driver, there are too many variables.
    if your mpg are 'low', you must find the cause, which is not necessarily the car, but might possibly be a part of it.
    the many external factors include weather, climate, topography, amount of starts and stops, average speed, top speed acceleration, and others.
    as for the car, tire size, pressures, tire make and model, air and cabin filters, oil level, can all be factors.
     
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  17. RCO

    RCO Senior Member

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    Hello from Cornwall UK. I have a 2016 Business Edition also and there is a high demand for fuel in the warm-ups and short trips of less than 5 miles. I wonder if your driving style has an impact and what temperature you set the heater at. Certainly, I would recommend you leave the car to decide when to activate EV, but if your tyre pressure is slightly higher than the book recommends you should have got better mileage over a 24mile trip. Can you say where in UK you are - your county or nearest city would be enough?
     
    #17 RCO, Feb 16, 2018
    Last edited: Feb 16, 2018
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  18. kithmo

    kithmo Couch Potato

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    I have heat set to around 21 deg C which gets a good score on the summary at the end of a journey.
    Ideally heat off, at least +5 psi in the tyres (some go even higher) and use the econometer on the MFD to achieve great mpgs.
    I feel that the ICE seems to warm up quicker when the heater is on.
     
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  19. 4est

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    If the heater is off, the ice stops at a lower temp, so less fuel used
     
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  20. RCO

    RCO Senior Member

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    I set my heater to 18.5°C on cold mornings. You'll still get heat once the ICE warms up and can increase as necessary later. South Wales is as far north as I seem to go these days, so perhaps that's why I never need more than 20°C . Well, that and the fact her ladyship prefers the car to be much cooler than I do! I'm averaging 65mpg (UK) ATM with mixed driving speeds and journeys types/distances.
    PS, no hypermiling!!!
     
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