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Thread: So, what am I missing with my fuel economy? 2018 5MT CDM Micra.

  1. #1
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    So, what am I missing with my fuel economy? 2018 5MT CDM Micra.

    55km one way trip. Vehicle is started and driven 2.3km at 60km/h in 5th gear. The next half is maintained at 85km/h in 5th, steady speed, slightly rolling hills but nothing requiring a downshift. The next half is held at 105km/h, flat and steady.

    -10C in the am, about 5C in the afternoon.

    No idle time whatsoever. The Mirage does this commute at 4.4l/100. The Micra is achieving 7.0 give or take.

    Seems a bit high to me, especially comparing all other results here, and I'm a hypermiler.

    Is it the cold? No block heater but I'm running a grille block. No idle, no drivethroughs, no AC, even keep the lights off when possible, tires maintained at 44psi. no nothing to cause me to hit above what most are getting. For the Mirage to get these numbers I would have to maintain 150/kmh.

    How do I get this thing below 7? Wait for warmer weather? Still seems high though for what it is.


        __________________________________________

        click to view fuel log View my fuel log 2018 Micra SV manual: 6.8 L/100 km ... 41.8 mpg (Imp) ... 14.8 km/L ... 34.8 mpg (US) ...


  2. #2
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    Note I am maintaining 5-10 under the posted limits as well, and not using cruise on the rolling hills because it's not efficient through that section.

        __________________________________________

        click to view fuel log View my fuel log 2018 Micra SV manual: 6.8 L/100 km ... 41.8 mpg (Imp) ... 14.8 km/L ... 34.8 mpg (US) ...


  3. #3
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    Also yes, it is an accurate 55km. GPS checked, speedo is maybe 1% under at worst. Car reads 55.3 for my 55.8 tracked commute. Live speed holding 100km/h reads 101 on my GPS.

        __________________________________________

        click to view fuel log View my fuel log 2018 Micra SV manual: 6.8 L/100 km ... 41.8 mpg (Imp) ... 14.8 km/L ... 34.8 mpg (US) ...


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    Any particular reason for running a grill block? It doesn't get cold enough to warrant one where you live and in the summer they can only stand to do damage to your vehicle if you leave them on. In the winter use a block heater.

    If it's for aero and to lower the drag coefficient, make sure you design some radiator passthrough, esp since you have an SV with AC.

    I get 6.8-7.2 in the winter in my 5MT but I drive it really hard and winter here is between -40 and -20 usually.

    Do you have the stock plug still connected that causes AC to start with your heater? If you're a hypermiler, you can disconnect the harness on the button that automatically turns it on. It's been well documented on here already about how much you can save not running AC with/without heat (~6% IIRC).

    Maybe there's an issue with your fuel gauge/sensor? Trying to hypermile it I can easily get around ~6.2L/100km in the cold.

  5. #5
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    Quote Originally Posted by spacewolf View Post
    Any particular reason for running a grill block? It doesn't get cold enough to warrant one where you live and in the summer they can only stand to do damage to your vehicle if you leave them on. In the winter use a block heater.

    If it's for aero and to lower the drag coefficient, make sure you design some radiator passthrough, esp since you have an SV with AC.

    I get 6.8-7.2 in the winter in my 5MT but I drive it really hard and winter here is between -40 and -20 usually.

    Do you have the stock plug still connected that causes AC to start with your heater? If you're a hypermiler, you can disconnect the harness on the button that automatically turns it on. It's been well documented on here already about how much you can save not running AC with/without heat (~6% IIRC).

    Maybe there's an issue with your fuel gauge/sensor? Trying to hypermile it I can easily get around ~6.2L/100km in the cold.

    -25 in the mornings is plenty of reason. That and I keep forgetting to order a block heater. Takes forever to heat up. I run the block in the morning only. Once we reliably get above -5 in the am I'll toss it in the shed.

    AC recently disconnected but I was always good about shutting it off immediately.

    As mentioned, odometer is accurate. My trip usage gauge is royally out to lunch but I use actual fill ups not what my optimistic car tells me.

        __________________________________________

        click to view fuel log View my fuel log 2018 Micra SV manual: 6.8 L/100 km ... 41.8 mpg (Imp) ... 14.8 km/L ... 34.8 mpg (US) ...


  6. #6
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    Record low for Squamish is like -17 unless you live up on one of the mountains. Then again, I've never been so what do I know


    A block heater will do way more for protecting and heating up your engine than a grill block. It's only particularly useful when it's freezing cold all day, every day for months (like above the arctic circle/Siberia) and your vehicle has trouble keeping temps while running and needs it to hold the extra heat in the engine bay. Like -40 to -60 all day. With good ol' global warming we get like a week of -40 tops up here (without windchill).

    Your engine is going to take as much work initially getting up to temperature after sitting all night with or without a grill block.
    The oil is going to be just as cold with the same amount of friction and there isn't going to be air flowing through the chassis.

    My 0.02$, start using a block heater all winter and for hypermiling spend a hot weekend designing aero to cover up a lot of open grill ensuring enough flow over your radiator when running your car hard in the summer.

    You can find the sweet spot for how much our cars actually need to breath to stay at an ideal operating temperature.
    I'm sure the rest of us here would love to know some hard numbers.

    I'm guessing you've probably already seen MetroMPGs post:
    https://micra-forum.com/showthread.p...ion-at-90-km-h

  7. #7
    Senior Member Azmodon's Avatar
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    The Cd of a mirage is 0.27, the micra is 0.32, so that's going to hurt, the mirage is also 500Lbs lighter, so once up to speed it'll cruise will less input.

    The radiator on our cars were designed to keep the engine cool in the thin hot air of Mexican mountains, so blocking half of it (the left 70% of the lower grill, and 100% of the upper grill) should have no appreciable effect for us.

    All cars (to my knowledge) have a mechanical thermostat, before the engine, and the coolant sitting in it, are up to temp, it is closed, coolant isn't flowing through the rad or the heater core (hence having the "heat" on with a cold engine results in cold air being blown, as soon as you hear the engine warm up and drop rpm, the thermostat has opened and you suddenly start getting warmer air). If you submerged the rad in liquid nitrogen (and the coolant didn't go solid), the engine would heat up in the same amount of time as if it wasn't... the thermostat would likely close again as its temperature dropped though lol

    One of the biggest issues to me is tire compound (rolling resistance of it), same size, pressure etc, same car - swapping tire brands can dramatically change fuel consumption, including how that compound deals with different temperatures.

    One thing to look at is also how you accelerate - look up the torque curves for the two engines you're used to, see if they overlap? The HR16DE starts to level off at 2400, peaking around 3200, so trying to accelerate below that window may see you spending so long ramping up that you consume more than going slightly faster.

    Aside from that, the how and why of getting your micra lower could be any one of a dozen things, from air dams below the bumper, to a flat floor, or swapping out a sticky pulley, ride height inconsistancy from factory... whether your drive is mainly north/south, since the aerodynamic lateral profile of a micra is basically a brick...

        __________________________________________

        click to view fuel log View my fuel log 2015 Micra SV automatic: 7.1 L/100 km ... 39.9 mpg (Imp) ... 14.1 km/L ... 33.3 mpg (US) ...


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    HammyJ (12-19-2021),MetroMPG (03-22-2019)

  9. #8
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    Well, today's high is minus 2. Guess I've been so used to the cold that I thought it was warmer during the day than it actually has been. Which means I'm more willing to accept numbers in the low 7s. For now.

    Since Squamish was brought up... many times as a criticism of my intellect, I've recently moved to Saint Paul de Kent, NB. So while the "you dont know your weather or speed limit" comments are all pointless, I will accept criticism for not changing my location.

        __________________________________________

        click to view fuel log View my fuel log 2018 Micra SV manual: 6.8 L/100 km ... 41.8 mpg (Imp) ... 14.8 km/L ... 34.8 mpg (US) ...


  10. #9
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    I'm not sure if moving to New Brunswick helps that case haha. I'd take almost anywhere in BC over the east coast any day.
    Source: From Labrador, grew up in Halifax, went to college in Newfoundland.

    It's not about "you don't know" just that hyperbole is a real problem on the internet and those 3 lines in your profile are all we know about you when trying to solve for a complex problem.

  11. #10
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    I did some testing on my end the last two days since replying to this thread.
    It's been -5 to +5 here (all the wind bringing in some warmth from the Pacific).

    Average on my 2017 SV 5MT:
    - 6.4L/100KM trying to hypermile

    Route to work/home:
    11Km trip (22 round) x 4 = 88Km Total

    Other factors:
    - Temp between -5 and +5
    - Altitude 2100-2200ft
    - Studded winter tires still on
    - Wind 35-65km/h
    - Custom CAI (everything else stock)
    - Stock 15x5.5 steelies, winter tires @33PSI



  12. The Following 2 Users Say Thank You to spacewolf For This Useful Post:

    HammyJ (12-19-2021),MetroMPG (03-22-2019)

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