Great mpg in HV mode - 2018 Honda Clarity Forum
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post #1 of 20 (permalink) Old 01-30-2020, 05:58 PM Thread Starter
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Great mpg in HV mode

Recently finished a full tank of gas running exclusively in HV mode; got 50.7 mpg which I think is great for this car. The battery always had some charge from me plugging in each night, so going to try HV again without any battery charge to see what happens.
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post #2 of 20 (permalink) Old 01-31-2020, 01:02 AM
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Originally Posted by MPG+ View Post
Recently finished a full tank of gas running exclusively in HV mode; got 50.7 mpg which I think is great for this car. The battery always had some charge from me plugging in each night, so going to try HV again without any battery charge to see what happens.
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Seems like most folks report 45 to 50 mpg in hv mode. Weather n driving habits drive the numbers some what.

In colder months I get in the high 40's and ~52 in the warmer months. I concur the Clarity gets great mileage given the size n comfort etc.

Enjoy!
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post #3 of 20 (permalink) Old 01-31-2020, 09:50 AM
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Recently finished a full tank of gas running exclusively in HV mode; got 50.7 mpg which I think is great for this car. The battery always had some charge from me plugging in each night, so going to try HV again without any battery charge to see what happens.
If you were plugging in each night then the 50 mpg is artificially high, although by how much you won't know until you run a tank in HV without plugging in. But even when you do that just one test won't be definitive because there will likely be other variables between the two tanks. But it should give you some idea.

In HV mode the battery is still used but of course gets recharged by ICE, but the battery level fluctuates by a few percent while you are driving. Anytime you are in HV there is a set point, sometimes called the target SOC which the system is trying to maintain, it uses the battery as needed until it drops a few percent below the set point then it charges it back up to the set point, and the cycle continues. When you turn off the car it will randomly be at some SOC which could be at the set point but more likely will be a little below. Then when you start the car again the current SOC will be the new set point. The same thing happens by the way when turning off HV while driving then immediately turning it back on again. This is known as HV reset and is used by some people on purpose to reduce engine noise especially when driving in the mountains.

For example if you leave the house at 100% then stop at the grocery store and turn off the car it might be at say 98% SOC. Then when you turn on the car 98% will be the new set point. When you get home and turn off the car it might randomly be at 97%. Since you are plugging then it will charge it from 97% to 100%. That's just an example it might be less than that usually, but over a tankful it will add up.

So even though you drove in HV for that tank you definitely used some grid electricity also, but there is no way to know how much unless you had uses the app to check the SOC level each time you arrived home, or do the test you are planning where you don't charge at all for a tank. Normally that type of test is done by filling up when you have 0 EV range, that way you don't have to constantly remember to press the HV button
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post #4 of 20 (permalink) Old 01-31-2020, 03:11 PM Thread Starter
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Good Points 2002

I thought the mpg was kind of high, given the cold temps here in CT, and figured the car would "go to the well" since there was plenty there, ha ha. So I will be testing again on a dry tank of electrons, knowing the mpg will likely change in the future due to climatic conditions and the types of trips I take. But at least it will sort of a benchmark for future comparisons.
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post #5 of 20 (permalink) Old 02-02-2020, 10:17 AM
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Given that the 2017 Volt and 2018 Clarity PHEV have very similar EPA ratings (2 MPGe difference and the same ICE MPG), I can believe OP was seeing HV mpg in the 50s. Unlike the Clarity, the Volt provides readouts for both EV and CS (Charge Sustaining or HV) mode MPGs and on those rare occasions where I take my Volt past battery range around Denver I see the ICE MPG well over 50 MPG. Yesterday I drove a little over 18 ICE miles beyond my battery range at 55 MPH and my Volt reported 56 MPG.
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2018 Honda Clarity Touring PHEV - Forest Green w/Tan interior (wife's car)
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post #6 of 20 (permalink) Old 02-06-2020, 10:19 AM
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Last fall with temps in the 50-60 degree range I drove my 2018 clarity touring from Dallas to Rapid City, SD, 1150 miles. The first 45 or so were on battery but after that all ICE. I had no wind to light tailwind over most of the trip. I kept a close record of fuel used and miles driven and I averaged 55.2mpg. Factoring the initial 45 elec battery miles and the battery assisted help from time to time I was still over 50mpg for the trip. I did no recharges along the way and other than fuel stops every 280-300 miles or so made no other stops. Sucks that this car has such a small gas tank but other than that, no complaints.
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post #7 of 20 (permalink) Old 02-06-2020, 10:23 AM
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Agree - the fuel tank is too small - almost motorcycle like?
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post #8 of 20 (permalink) Old 02-06-2020, 10:33 AM
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I should add to the above statement that the entire trip was driven at 65mph. I took another such trip and drove 75-80mph and only averaged 44mpg although I did have a little headwind on that trip. Still not bad for a full sized sedan but the little extra speed does effect the economy.
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post #9 of 20 (permalink) Old 02-06-2020, 07:15 PM Thread Starter
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MPG and temps

Good to hear your Clarity did so well under somewhat mild temps. Even if it wasn't a plugin, for its size I think it beats a lot of cars on straight mpg.
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post #10 of 20 (permalink) Old 02-10-2020, 11:49 AM
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I would never get those mpg on long trips. There is no way I can drive 65 mph for that long. I wonder what one could expect going 80-85 for an extended duration of time? Has anyone done that?

2018 Clarity plug in- Base (Silver)
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