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Discussion Starter · #1 ·
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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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.
MGP+

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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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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Discussion Starter · #4 ·
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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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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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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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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Discussion Starter · #9 ·
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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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?
 

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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?
I've found that the posted speed limit +2 is the maximum safe speed on many long haul interstates. This is where I set my cruise control and invariably when I see someone pulled over they have passed me, even if my only a single MPH. So if the speed limit is 65, don't go over 67 on rural interstates. If the speed limit is 75 (Colorado) or 85 (Utah & Texas), don't go over 77 or 87 MPH. +2 has the added benefit that you can tap down one mph and then you're definitely in the speed variance range without looking like you slammed on your brakes.

Urban interstates are a completely different story. Stick to the flow of traffic or maybe slightly slower if it's above the speed limit. You don't want to stand out to the officer running their radar gun.
 
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Discussion Starter · #12 ·
Updated MPG

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.
Just completed a "test", operating my Clarity with zero juice in the battery, in HV mode. 266 miles on 6.4 g works out to 41.6 mpg, which I think is great with CT's winter climate and rolling hills. That's pretty good, moving a 2 ton car around for 266 miles, part highway and part secondary roads. EV kicked in whenever it could. :smile_big::smile_big::smile_big:
 

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I've found that the posted speed limit +2 is the maximum safe speed on many long haul interstates. This is where I set my cruise control and invariably when I see someone pulled over they have passed me, even if my only a single MPH. So if the speed limit is 65, don't go over 67 on rural interstates. If the speed limit is 75 (Colorado) or 85 (Utah & Texas), don't go over 77 or 87 MPH. +2 has the added benefit that you can tap down one mph and then you're definitely in the speed variance range without looking like you slammed on your brakes.

Urban interstates are a completely different story. Stick to the flow of traffic or maybe slightly slower if it's above the speed limit. You don't want to stand out to the officer running their radar gun.
I use the waze app to find police radaring. :) Just wondered if anyone had mpg numbers going 70+ for extended persion of time. I was going to try it myself but had to plug it in after a night of not doing it! haha
 

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You can expect the MPG to drop as you go faster. The Volt drops to about 40 MPG at 70 MPH. I think the Clarity will drop to around 40 MPG based on driving across I-70.
 

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I got 34 mpg going upper 70's on a trip recently. Sometimes I hit low 80's. Mostly highway. I guess that isn't too bad. this is after I charged the car and went completely in HV mode.
Using heat as well with weather in 30's.
 

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I got 34 mpg going upper 70's on a trip recently. Sometimes I hit low 80's. Mostly highway. I guess that isn't too bad. this is after I charged the car and went completely in HV mode.
Using heat as well with weather in 30's.
In HV using the heater shouldn't be a factor since it gets heat from the engine via heater hoses just like a regular car. At least on the highway where you have steady engine heat.

In city driving in HV in cold weather if you spend some time driving very slow or stopped at a light the engine will sometimes stay running just to provide heat. More than once I noticed the engine running while I was stopped at a light, I turned off climate and ICE immediately shuts off. Turn climate back on, ICE immediately comes back on. So that's a little more gas used in that situation but it's basically idling and I assume also doing a little bit of battery charging while it's at it.

On the highway, even though ICE sometimes shuts off while cruising at freeway speeds like when you have a slight downhill, I wouldn't think it would be off long enough for the coolant temperature to drop that much.
 

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In HV using the heater shouldn't be a factor since it gets heat from the engine via heater hoses just like a regular car. At least on the highway where you have steady engine heat.

In city driving in HV in cold weather if you spend some time driving very slow or stopped at a light the engine will sometimes stay running just to provide heat. More than once I noticed the engine running while I was stopped at a light, I turned off climate and ICE immediately shuts off. Turn climate back on, ICE immediately comes back on. So that's a little more gas used in that situation but it's basically idling and I assume also doing a little bit of battery charging while it's at it.

On the highway, even though ICE sometimes shuts off while cruising at freeway speeds like when you have a slight downhill, I wouldn't think it would be off long enough for the coolant temperature to drop that much.
True! I am not sure why I wrote with heat! :)
 

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True! I am not sure why I wrote with heat! :)
Well cold weather does affect all cars including gasoline powered. And even more so vehicles like Clarity that have to make up any shortcomings in engine heat by using a resistance heater to heat the cabin. Some other PHEV's have a heat pump which is more efficient than a resistance heater, however that means a couple more parts to squeeze into the engine compartment, and they still need a resistance heater for when temperatures drop too far below freezing, so it all adds to the complexity, Honda decided to keep cost and complexity down by having only a resistance heater, although we do pay for it via more electricity needed to heat the car when ICE is not running.
 

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Tank is small, but so is my bladder.

Agree - the fuel tank is too small - almost motorcycle like?
I’m new to the forum and still driving a ‘14 Avalon Hybrid with a 17gal tank. At 75mph in the mountains I’m getting around 34mpg which would take me around 7.7 hours. There’s no way I can do that much time without a rest stop.

The 7gal tank on the Clarity should easily make it for for 300mi @ 65mph (4.6+hours), I usually need a pit stop at around 4 hours or so; much more humane than waiting my car’s big tank is empty before I get to empty my own. Four and a half hours would be perfect synchronicity! It’s not a bug, it’s a feature for me.

(P.S. I used to ride an R60US. On a bike 250 miles was the right time to stop and stretch your legs, even as a 20 year old)
 

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I got 34 mpg going upper 70's on a trip recently. Sometimes I hit low 80's. Mostly highway. I guess that isn't too bad. this is after I charged the car and went completely in HV mode.
Using heat as well with weather in 30's.
34 mpg is kind of AWFUL for a Clarity! Most of my driving is on interstate highways at 70-74 mph and I'm averaging 48 mpg in HV mode. On a 1200 mile trip north in October at speeds mostly between 60 and 65 I averaged 46 mpg in HV mode, starting with a full battery and arriving at 2/3 capacity.
 
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