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Discussion Starter · #1 ·
Hello, fellow Clarity owners! My name is Maurice, and this is my first Clarity post. I have experience with sites such as M35forum.com and headfi.org, and it was fun posting about DYI projects on the M35, and posting audio reviews on headfi.org. I purchased/leased the 2018 Honda Clarity Plug-in hybrid Touring new, and was happy to not only use a car with over 45 miles of EV-only range, but also use a car with over 300 miles of HV (gas range) as well!

Fast forward two and a half years, and not only does my battery usually get about 35-40 EV range (not too worried about that as I can check the EV battery capacity in the near future), but much more concerning to me is a possible degradation of the HV range. I used to get a HV range of about 310 miles (should have probably been more than that!) to as low as 199 miles as of last night is disconcerting, in my opinion. My possible reasons for the degradation could be that since I have not been charging the car with my usual means of the combination of public and home Juicebox chargers, and using the HV charge mode to charge the car as a replacement of charging with the traditional chargers - mainly since I have been in the middle of a move to a new house for over a month. I am not sure if these are the reasons why my HV range has decreased dramatically. I took the Clarity in for service about a year ago when the HV range was showing too high - their software update fixed the issue. Then I had issues about the HV range being too low (about 211 HV range). After taking it in, the dealer performed a complete reset of the system, and that fixed the range issue. For about one gas tank refill. Once I went back to using the car's HV charge mode to charge the car, the HV's range went lower and lower, to the lowest 199 HV range from a filled gas tank last night.

Does anyone have a reason or reasons why the HV range would show so low, and what fix there can be (besides completely resetting the system after every fill up)?

Thanks for your assistance in advance!

225 HV before "full reset"
225_HV.jpeg


199 HV after "full reset" and one gas tank full
199_HV.jpg
 

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What is your actual HV range? Not what the guess-o-meter predicts on the display, but how many miles do you actually get per gallon? Since you aren't charging at the moment you can obtain this at each fill up by dividing the number of miles driven since the last fill up by the gallons of gas purchased. A more accurate mpg is obtained after three tankfuls by dividing the total number of miles driven for those three tankfuls by the total gallons of gas purchased.

Since you mentioned using HV Charge as a possible reason for your lower mpg you would want to isolate that, i.e. go three tankfuls with HV Charge and three tankfuls without HV Charge and see if that makes a difference. Just make sure that you are at 0 EV miles when you fill up, because if you fill up when you still have some EV miles remaining from HV charge that will throw off the mpg calculation.
 

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FIrst, what is your HV range without using HV Charge mode? HV Charge mode is guaranteed to burn more gas than HV mode, but I don't think it's going to be a third more.
 
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Discussion Starter · #4 ·
What is your actual HV range? Not what the guess-o-meter predicts on the display, but how many miles do you actually get per gallon? Since you aren't charging at the moment you can obtain this at each fill up by dividing the number of miles driven since the last fill up by the gallons of gas purchased. A more accurate mpg is obtained after three tankfuls by dividing the total number of miles driven for those three tankfuls by the total gallons of gas purchased.

Since you mentioned using HV Charge as a possible reason for your lower mpg you would want to isolate that, i.e. go three tankfuls with HV Charge and three tankfuls without HV Charge and see if that makes a difference. Just make sure that you are at 0 EV miles when you fill up, because if you fill up when you still have some EV miles remaining from HV charge that will throw off the mpg calculation.
Thanks for the tips! I'll try filling up the tankfuls with HV Charge and three tankfuls without HV Charge of and see if those are making a difference. My thinking is that the HV Charge mode is really burning a lot of gas.

FIrst, what is your HV range without using HV Charge mode? HV Charge mode is guaranteed to burn more gas than HV mode, but I don't think it's going to be a third more.
Usually my HV range was the normal 300-310 mile range without using HV Charge mode, but you are onto something where the HV Charge mode is burning more gas (might be near a third more! 😭). It's probably burning more gas, even when the car isn't moving, i.e. while the Clarity is parked.
 

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Discussion Starter · #5 ·
My update with the Clarity's fuel gauge degradation is as such:

Each subsequent refueling with gas resulted in around a 199-at most 225 HV range after about 2 refuels to full.

225 HV range (most after 2 refuels of gas to full)
225_HV.jpeg

With the HV Charge mode used right after I received the car from a complete reset, I averaged only 23 miles per gallon.

Average Fuel: 23.2 mpg
updated fuel mileage-23mpg.jpg


Showing fuel mileage trends (less than 30mpg) - no bueno (for me, at least) after using HV Charge mode!
gas mileage cycles.jpg


According to my local Honda dealership (Scott Robinson Honda, Torrance), the service tech said the only way to temporarily fix the fuel gauge degradation issue was to perform a complete reset of the system. They also stated there is no timeline for when (or if) Honda will fix the fuel gauge degradation issue via software update, or otherwise (recall).

I am not sure how many Clarity's are affected by this fuel gauge degradation, but for those who have experienced this, the only way to rectify the issue, is to take it to the dealer and have them perform a complete reset of the system.

After complete reset of the system, back to normal, for now...
after complete reset.jpg


As of 6/13/2021 Also, when you receive the car, DO NOT engage HV Charge mode, or your fuel gauge may instantly lose a lot of HV (gas) range. I have already found out, that for my specific situation, the moment I engage HV charge mode, I will INSTANTLY lose at least 150 miles+ of HV (gas) range.

I will forward this forum thread to Honda, and hopefully they can take a look at the fuel gauge degradation issue and rectify it through a software/hardware update. I really want to buy out this car (lease) as it has been relatively pain-free, and has been great to use EV with a gas engine as a backup. I'd like to stay a loyal customer!
 

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My update with the Clarity's fuel gauge degradation is as such:

Each subsequent refueling with gas resulted in around a 199-at most 225 HV range after about 2 refuels to full.

225 HV range (most after 2 refuels of gas to full)

With the HV Charge mode used right after I received the car from a complete reset, I averaged only 23 miles per gallon.

Average Fuel: 23.2 mpg


Showing fuel mileage trends (less than 30mpg) - no bueno (for me, at least) after using HV Charge mode!


According to my local Honda dealership (Scott Robinson Honda, Torrance), the service tech said the only way to temporarily fix the fuel gauge degradation issue was to perform a complete reset of the system. They also stated there is no timeline for when (or if) Honda will fix the fuel gauge degradation issue via software update, or otherwise (recall).

I am not sure how many Clarity's are affected by this fuel gauge degradation, but for those who have experienced this, the only way to rectify the issue, is to take it to the dealer and have them perform a complete reset of the system.

After complete reset of the system, back to normal, for now...


As of 6/13/2021 Also, when you receive the car, DO NOT engage HV Charge mode, or your fuel gauge may instantly lose a lot of HV (gas) range. I have already found out, that for my specific situation, the moment I engage HV charge mode, I will INSTANTLY lose at least 150 miles+ of HV (gas) range.

I will forward this forum thread to Honda, and hopefully they can take a look at the fuel gauge degradation issue and rectify it through a software/hardware update. I really want to buy out this car (lease) as it has been relatively pain-free, and has been great to use EV with a gas engine as a backup. I'd like to stay a loyal customer!
Nowhere in your message do you indicate whether you followed the advice to track your actual miles driven based on the odometer and the number of gallons gas purchased to determine your actual miles per gallon and actual HV range.

The displayed HV range is an estimate, it is trying to predict your future mpg based on recent drives. Resetting the system merely clears that past history, and yes that will change the estimate since after a reset it no longer has any recent history.

When driving on a long trip it is much safer to only look at the actual fuel gauge, which by the way appears in none of your screenshots. The fuel gauge is the bars on the right side of the instrument panel, and is a pretty accurate depiction of how much fuel that you have left, it is not an estimate. It's like the fuel gauge that we have used for decades in our cars, and while fuel gauges are not perfect, it is still the most reliable method for determining how much further you can go on your remaining fuel. Of course like any fuel gauge it is only meaningful when you know your actual mpg, which again can only be determined based on tracking odometer miles and gallons pumped.

Also, when you receive the car, DO NOT engage HV Charge mode, or your fuel gauge may instantly lose a lot of HV (gas) range. I have already found out, that for my specific situation, the moment I engage HV charge mode, I will INSTANTLY lose at least 150 miles+ of HV (gas) range.
In fact there are several people who have done ACTUAL testing of their HV range and have confirmed that HV Charge is very efficient, and there is little loss of MPG. While HV Charge is running it is using more gas, but it is building EV range which can be used later, so in the end there is very little overall effect on mpg. HV Charge is a very useful feature that enables building up EV range for later use like city driving or hill climbing when you don't have an opportunity to charge.
 

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Discussion Starter · #7 ·
Nowhere in your message do you indicate that you followed my advice to track your actual miles driven based on the odometer and the number of gallons gas purchased to determine your ACTUAL miles per gallon and ACTUAL HV range.

Instead you continue to put all of your confidence in the estimates that the display shows you and the cars calculated MPG. Is there a reason why you do not trust actual data? Meaning the number of actual miles driven as shown on the odometer divided by the number of gallons pumped. Until you do this you have no idea whether you have a real problem or not. Personally I think the only problem that you have is over worrying about nothing. That may sound harsh, but until you come up with ACTUAL data about your fuel use you are creating concerns for yourself and others that are very likely nonexistent.

The HV range estimate is an ESTIMATE, it is trying to predict your FUTURE mpg based on recent drives. Resetting the system merely clears that past history, and yes that will change the estimate since after a reset it no longer has any recent history.

Since the HV range estimate is bothering you I suggest that you don't look at it, and only look at the actual fuel gauge, which by the way appears in none of your screenshots. The actual fuel gauge is the bars on the right side of the instrument panel, and is an accurate depiction of how much fuel that you have left, it is not an estimate. It's like the fuel gauge that we have used for decades in our cars, and while fuel gauges are not perfect, it is still the most reliable method for determining how much further you can go on your remaining fuel. Of course like any fuel gauge it is only meaningful when you know your ACTUAL mpg, which I certainly hope that you will start tracking.


This is really bad advice to give other owners, because again it is based on NO actual data. In fact there are several people who have done ACTUAL testing of their HV range and have confirmed that HV Charge is very efficient, and there is little loss of MPG. While HV Charge is running it is using more gas, but it is building EV range which can be used later, so in the end there is very little overall effect on mpg. HV Charge is a very useful feature that enables building up EV range for later use like city driving or hill climbing when the owner does not have an opportunity to plug in to charge the battery. It is normally not needed in ordinary driving, but it is a very useful feature at times, so you should not be telling other owners not to use it just because of your interpretations of what you see on your instrument panel.

I realize that you are trying to be helpful and share your discoveries with others, but you also came on here asking for advice, and if you ignore the advice you won't be helping yourself. I also suggest that you read other threads about HV Charge and HV range to find out from others what their experiences are.
Thanks for your assistance thus far! As for units of gas to miles driven, I inputted 4.372 gallons of gas to drive around 200 miles before refueling with 4.179 gallons of gas to drive around 220 miles before refueling to full again with another 5.387 gallons of gas.

There is a definite issue with the fuel gauge! I would never try driving to zero thinking that I have more range, when in fact, I don't. Here's a screenshot via HondaLink that is showing I have 71 miles left in the gas tank:

71 miles of range left (at about 38% of total fuel gauge [before full reset]) - should have been around 134.9 or so (38% of 355 [after full reset])
Fuel Gauge reading.PNG


I could see if Honda themselves told me I have zero issues with the fuel gauge (they did not), but both times I took the Clarity in for service, did they admit the fuel gauge degradation issue was something they had no immediate fix for! As of 6/13/2021 I will take Honda's word for it that there is something wrong, and I hope they will fix it!
 

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As for units of gas to miles driven, I inputted 4.372 gallons of gas to drive around 200 miles before refueling with 4.179 gallons of gas to drive around 220 miles before refueling to full again with another 5.387 gallons of gas.
Thanks for posting some actual numbers so that we can calculate what your Clarity's actual fuel efficiency is.

If I understand correctly you started by filling the tank with 4.372 gallons. Since we don't know how many miles were driven prior to that first fillup, then we just consider that a full tank, and disregard the number of gallons pumped. Next you drove for 200 miles and then filled up with 4.179 gallons. This calculates to 48 mpg. Next you drove for 220 miles and filled up with 5.387 gallons. This calculates to 41 mpg. Presumably there were some differences in driving conditions between those two tankfuls.

Putting the two tankfuls together, you drove a combined 420 miles on 9.566 gallons of gas, which calculates to 44 mpg for the two tankfuls. This indicates that your Clarity is functioning quite normally as far as gas efficiency in HV mode.

I would never try driving to zero thinking that I have more range
As long as you have plenty of EV miles remaining there is no risk in letting HV range go to zero, as you can then switch to EV to get to a gas station. I am of course talking only about city driving where gas stations are always nearby, not while on a road trip. However you said you cannot charge right now, but even so you can still calculate a pretty accurate actual range estimate based on your mpg. Like most cars, empty on the Clarity fuel gauge is not really empty, it seems at empty there is still about half a gallon left, at least that is my experience when I have refilled at empty. So if we think of that half gallon as about 20 miles of reserve fuel that we should avoid using except in an emergency, then realistically a tankful on the Clarity is about 6.5 gallons.

Your first tankful was 48 actual mpg, so your calculated range on that tank is 48 x 6.5 = 312 miles. On your second tankful which was 41 actual mpg, your range was 41 x 6.5 = 266 miles. Your average range on the two tanks was 44 x 6.5 = 286 miles. All of these are normal ranges for the Clarity, depending as always on driving conditions. So it seems that you do not have a problem with actual HV range in your Clarity.

There is a definite issue with the fuel gauge
You are confusing the discussion by using the term "fuel gauge" when you are really talking about HV range estimate. That's not just my opinion, it's what the term fuel gauge has always meant. If you look it up the definition is "an instrument used to indicate the amount of fuel in a fuel tank". It is not a range estimate, it is a volume indication.

That is the terminology used by Honda also, this is copied straight form the Clarity owners manual. The green box that says "Fuel Gauge" is how it looks in the owners manual, I did not add that.

Clarity fuel gauge.PNG



'
Clarity range.PNG



It is extremely rare in a modern car for a fuel gauge to be inaccurate, and you have so far not provided any evidence that your Clarity's fuel gauge is defective. It's a simple test really, if for example your fuel gauge reads 50% then you would expect that filling the tank will take approximately 3.25 gallons. Only if it varies wildly from that would there be a problem with the fuel gauge.

Some people have observed that if the gas tank is nearly full, that if they fill up the fuel gauge does not immediately show as full but remains where it was. But since most people don't fill up until the tank is about half full or less that's not an issue.

71 miles of range left (at about 38% of total fuel gauge [before full reset]) - should have been around 134.9 or so (38% of 355 [after full reset])
I have no reason to dispute your evidence that your HV Range Estimate is inaccurate. It's why I only use the HV range estimate around town, to give me a ballpark idea when I should fill up, although I can just as easily do this using the fuel gauge. On a road trip however I will only be looking at the fuel gauge and doing my own range calculations based on my known actual mpg.

I took the Clarity in for service, they did admit the fuel gauge degradation issue was something they had no immediate fix for! As of 6/13/2021 I will take Honda's word for it that there is something wrong, and I hope they will fix it!
The only service bulletin that I am aware of is for early 2018 Clarities which would sometimes show extremely high HV range, crazy numbers like 500 miles. For people who had that problem a software patch is available.
 

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Discussion Starter · #9 ·
Thanks for posting some actual numbers so that we can calculate what your Clarity's actual fuel efficiency is.

If I understand correctly you started by filling the tank with 4.372 gallons. Since we don't know how many miles were driven prior to that first fillup, then we just consider that a full tank, and disregard the number of gallons pumped. Next you drove for 200 miles and then filled up with 4.179 gallons. This calculates to 48 mpg. Next you drove for 220 miles and filled up with 5.387 gallons. This calculates to 41 mpg. Presumably there were some differences in driving conditions between those two tankfuls.

Putting the two tankfuls together, you drove a combined 420 miles on 9.566 gallons of gas, which calculates to 44 mpg for the two tankfuls. This indicates that your Clarity is functioning quite normally as far as gas efficiency in HV mode.



As long as you have plenty of EV miles remaining there is no risk in letting HV range go to zero, as you can then switch to EV to get to a gas station. I am of course talking only about city driving where gas stations are always nearby, not while on a road trip. However you said you cannot charge right now, but even so you can still calculate a pretty accurate actual range estimate based on your mpg. Like most cars, empty on the Clarity fuel gauge is not really empty, it seems at empty there is still about half a gallon left, at least that is my experience when I have refilled at empty. So if we think of that half gallon as about 20 miles of reserve fuel that we should avoid using except in an emergency, then realistically a tankful on the Clarity is about 6.5 gallons.

Your first tankful was 48 actual mpg, so your calculated range on that tank is 48 x 6.5 = 312 miles. On your second tankful which was 41 actual mpg, your range was 41 x 6.5 = 266 miles. Your average range on the two tanks was 44 x 6.5 = 286 miles. All of these are normal ranges for the Clarity, depending as always on driving conditions. So it seems that you do not have a problem with actual HV range in your Clarity.


You are confusing the discussion by using the term "fuel gauge" when you are really talking about HV range estimate. That's not just my opinion, it's what the term fuel gauge has always meant. If you look it up the definition is "an instrument used to indicate the amount of fuel in a fuel tank". It is not a range estimate, it is a volume indication.

That is the terminology used by Honda also, this is copied straight form the Clarity owners manual. The green box that says "Fuel Gauge" is how it looks in the owners manual, I did not add that.

View attachment 708


' View attachment 709


It is extremely rare in a modern car for a fuel gauge to be inaccurate, and you have so far not provided any evidence that your Clarity's fuel gauge is defective. It's a simple test really, if for example your fuel gauge reads 50% then you would expect that filling the tank will take approximately 3.25 gallons. Only if it varies wildly from that would there be a problem with the fuel gauge.

Some people have observed that if the gas tank is nearly full, that if they fill up the fuel gauge does not immediately show as full but remains where it was. But since most people don't fill up until the tank is about half full or less that's not an issue.


I have no reason to dispute your evidence that your HV Range Estimate is inaccurate. It's why I only use the HV range estimate around town, to give me a ballpark idea when I should fill up, although I can just as easily do this using the fuel gauge. On a road trip however I will only be looking at the fuel gauge and doing my own range calculations based on my known actual mpg.


The only service bulletin that I am aware of is for early 2018 Clarities which would sometimes show extremely high HV range, crazy numbers like 500 miles. For people who had that problem a software patch is available.
Of course Honda wouldn’t want to actually publicly publish an issue with the Clarity plug-in hybrid’s HV range, fuel gauge, et cetera (the issue I was experiencing). Most evident my latest post that stated numbers and my experience was invisible to normal viewers for several days (what is Honda hiding!?)

I want to buy out the car out of my lease (Honda is discontinuing ALL Clarity versions this year Here), but not having issues like this resolved worries me to the point of unfortunately considering similar/more range option(s).
 

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Of course Honda wouldn’t want to actually publicly publish an issue with the Clarity plug-in hybrid’s HV range, fuel gauge, et cetera (the issue I was experiencing). Most evident my latest post that stated numbers and my experience was invisible to normal viewers for several days (what is Honda hiding!?)

I want to buy out the car out of my lease (Honda is discontinuing ALL Clarity versions this year Here), but not having issues like this resolved worries me to the point of unfortunately considering similar/more range option(s).
Honda doesn’t run this forum so I pretty sure they’re not censoring your posts.
 

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Of course Honda wouldn’t want to actually publicly publish an issue with the Clarity plug-in hybrid’s HV range, fuel gauge, et cetera (the issue I was experiencing).
The issue that you experienced was not with HV range because based on the numbers that you provided you get an average of 286 miles of HV range which is quite good considering the small gas tank of the Clarity. And you are getting an average of 44 mpg which is really good for a car the size of the Clarity. And you do not have an issue with the fuel gauge, at least you have not presented any evidence of this as I indicated in my previous post.

You have only presented evidence that you are getting inaccurate HV range estimates, which is not unusual or unexpected since HV range estimates are just that, estimates.

The information that you have provided relating to actual mileage and actual gas consumption indicates that your Clarity is functioning perfectly normal in terms of fuel efficiency and HV range. Your concerns are related to the HV range predictions that your car gives you. Car ownership is certainly a personal choice, and if accurate range predictions is very important to you then hopefully when your lease expires you can find a car that provides more accurate range estimates to replace your Clarity.
 

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Discussion Starter · #12 ·

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  • ClarityForum.com is an independent Honda enthusiast website owned and operated by VerticalScope Inc. Content on ClarityForum.com is generated by its users. ClarityForum.com is not in any way affiliated with Honda Motor Company
 

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I don’t know about degradation, I just think the math is does is funky. We’ve owned a Clarity PHeV for 2 years now and on several occasions I confirmed that if you add just a tiny bit of gas into the tank neither the gauge nor the guess-o-meter will reflect it. For instance we drive it 99.9% electric, so a tank of gas will last us well over a year.

Gas starts degrading after 6 months and I don’t want old gas sitting in there, therefore we don’t get full tank. But putting in just like a gallon (which is 15% of the tank capacity) does not increase the range guess-o-meter nor adds any ticks to the fuel gauge.

Resetting the car, which you can do yourself by disconnecting the battery, does update both. But without reset, even driving several hundred miles it won’t update.

this could be just how they do the math, if you never drive on gas (hv) then it never updates the calculations to take into account that it has more gas now. But I do think the fuel gauge should increase. But it doesn’t. You have to put in like half a tank more than is in there now for it to reflect.

this is easily repeated by taking a 1 gallon can of gas, filling it up and putting into clarity. Clarity will act as if nothing happened.
 
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