Fuel Consumption Question

K

Kyle’s Clarity

Member
I just had a strange experience and I’m wondering if anyone can shed some light. I just completed a roughly 140km round trip. 70km to the destination in the morning and 70km back home in the evening. Weather is below freezing but I don’t think it’s a huge factor.

I left this morning with probably between 2/3 and 3/4 of a charge and a full tank of gas. Knowing I was going into this with a lower than preferred starting charge, I started my commute in ECON mode until I left the city and then ran HV Charge for a little while before switching to HV mode. I drove the remainder of the highway commute in HV mode (ICE ran the entire time far as I can tell) until I arrived at the destination town and switched off HV for the remaining handful of kms. I was able to add about 3Kwh to the battery at a Level 2 charger over lunch, topped off the gas tank ($7 worth) and then drove back the same route.

The drive back was in HV ECON from as soon as I left the gas station until I arrived back at my home town and then I drove the last 8 or 10kms with HV off. The ICE seemed to be on the entire highway portion of the drive. It maintained my estimated remaining EV kms (within about 2 or 3kms) and the final 10km drive consumed about 6km of estimated EV distance.

The strange thing that really stood out to me though, was that I still showed a full tank of gas. I know the reading can take a bit to stabilize and it did drop a bar and go back up to full during the drive but I just drove between 50 and 60kms with the ICE running the entire time in subzero temperatures with the heater and heated seat going and apparently used an imperceptible amount of fuel. Does this sound right to anyone?


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Yes. At only 50km you didn’t drive very far. The drop in fuel level simply hasn’t registered in the gauge yet.
 
When the ICE is running, it supplies the heat as a byproduct, like regular old gas-only cars. The gas gauges on many cars don't show any gas usage for a while after you fill the tank. I see this behavior on our Clarity PHEV.
 
Ditto on what @craze1cars said. My fuel gauge is very slow to respond. See if it changes tomorrow. 50 kM should be about a gal since it’s running a lot due to low temp. One would expect a gal (~4 liters? for you Canadians) to register on the gauge if it wasn’t over filled to start with. I accidentally over filled mine due to the slow response of the gauge and it ran quite a bit before I lost a bar. Could this have happened to you? Please let us know if it changes tomorrow.
 
Thanks for the input everyone!

@craze1cars The reason that this stood out was because the drive in the other direction knocked off like 3 bars. It seemed like a substantial inconsistency.

@KentuckyKen I’ll probably be going out again later this evening so I’ll see if there’s any notable change tonight and if not, tomorrow.


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MPower said:
Could the high usage in the other direction be the result of the time you were driving in HV Charge?
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I suppose it’s possible. I hadn’t considered that so thanks for pointing it out.

Also, I did end up going out again tonight and the car is still reading a full tank of gas. Maybe I really did just use an imperceptible amount of gas over that 50km drive. If that’s the case, I’m not complaining haha.


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HV Charge is a very wasteful mode. Very evident if you put it in instant MPG mode on the screen. In my experience it gets about 25 mpg during those times. I still have not found a single practical use for that mode and recommend everyone avoid it like the plague. Compared to that if engine is running at low rpm just to generate heat and nothing else due to cold temps it gets around 60 mpg in my experience experience.

So yeah I’d say if you used HV charge mode in one direction and not the other, you could have very well used 2.5x more gas one direction.

Don’t use HV charge. It’s wasteful. Always.
 
Maybe not always. I have found one situation, and only one, where HV Charge is worth it for me.
If you’re ever facing a long and significant climb and you’ve inadvertently let your SOC run down then it’s worth the reduced efficiency to run it to build up the SOC for the climb. This strategy will make the drive uphill much more pleasant and will help avoid the angry bees. And it will help avoid the loss of power scenario that a few unfortunate Claritys are experiencing.
Of course it’s best to switch to HV before hand while you have sufficient charge, but it’s still better to use HV Charge than hit a mountain climb with insufficient SOC.
@craze1cars is right in that outside this single senario, my utility rate would have to be unbelievably high for HV Charge to ever be economical.
 
I have used hv charge while going on a down hill grade of about 3 to 6 percent for about 18 miles. My ev range went from 9 miles to 24 miles. Average speed about 56mph. Simce i was going down hill the ice was only charging the battery a about 95 percent of the time. I was hyper miling to make sure i made it to the next gas station about 50 miles away. So in this case i gained overall range when hv charge shut off at its limit. I usually get about 40 mpg in hv mode at 70mph. This drops to 27mpg in hv charge. So even on flat ground i recoup most all of the lost fuel with the ev range gained via hv charge. I usually do this when i don't have a place and/or time to plug the car in and want to use ev mode in town.
 
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Ken: Loss of power scenario is simply a defective car. Mine is not defective, so I have found absolutely zero loss of power even driving hundreds of miles thru mountain ranges with a depleted battery. If someone needs to use HV Charge to work around the defect in their car, that sounds like an effective and unfortunate temporary work-around until Honda can fix the car.

As for subjectivity of angry bees and a more pleasant drive...well...as has been discussed dozens of times...that's subjective. We all know HV Charge mode raises rpms higher than they would normally be. So what's the net gain of making a level-land cruise LESS enjoyable by raising rpms for that stretch, just to avoid a raising of RPMS while going up a hill later? Hmmm....again...subjective. Opinions vary.

As for Neal's scenario...I'm frankly not convinced of that math on that trip. It would be interesting to see what overall mpg on a trip like you describe would have been, had you just let the car do it's thing, and left it go in HV without the charge mode. I understand you thought you were maximizing mileage. But were you? Travelling downhill for 18 miles in regular HV mode at 56 mph likely could have yielded 60 to maybe 80 mpg with engine even shutting off many times. So I'm not finding how forcing into HV Charge mode and reducing that downhill run to 27 mpg steady run instead would provide true a net gain and actual saved gas, despite gaining a reported 15 miles of EV range. As someone who finds the displayed mpg, estimated ranges, estimated mpg, etc to be woefully inaccurate on this car, I'd need to see it with actual figures by comparing odometer to gallons taken at the pump on back-to-back drives, and I know that's not usually a realistic experiment for anyone. But I've often checked what the dash says is happening with this car by using a basic calculator, and many times my manual calculations have shown the dash to be substantially off. Usually by 10%ish. Sometimes 20% or more. This goes for MPG, and estimated EV and HV ranges.

Note that on my mountain runs, for downhill runs, I'd often put it in EV mode...and for an 18 mile downhill mountain run I'd actually gain 10 to 15 miles of EV range by the time I got to the bottom, gaining 3 to 4 bars on the electric gauge. So gravity charges this car on long downhills too, with engine completely shut off. I couldn't fathom choosing HV Charge for this run, when gravity was charging the car for free, faster than the battery could even accept it, based on a chevron or two disappearing with paddle-shifter usage as I got toward the bottom and the battery was probably heating up.

I have personally found this car to be stunningly efficient by letting it do it's own thing in HV mode while driving with great spirit and fun through mountain ranges when looking at it from tankful-to-tankful perspectve, and not on a per-drive-according-to-the-dashboard-calculations perspective. I've measured mpg between 50 and 55 mpg running over 300 miles between fill-ups in extrtemely high-altitude mountainous terrain, by just leaving it in HV mode and never touching a button, other than occasionally forcing it to EV mode for very long downhills as a charging exercise. And at the same time I've measured mpg as low as 28 with cruise control set at 80 mph into a strong headwind tearing across the middle of the US. The mpg meter on the dash wasn't even remotely in the ballpark on either of these trips. I honestly think many are being very jaded with what they see as "facts" when they exclusively trust the dashboard displays for little 15 to 100 mile stints and commutes. The numbers to not often represent the truth...and I've seen them both over and under estimated depending on the drive.

I'll stick by my opinion. And it is only an opinion, as others will vary: HV Charge mode is a waste, and should never be activated. In many ways this car is actually smarter than we are.
 
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@craze1cars, thanks for all the data points. They are very helpful. You’ve got a great Clarity if it will go up mountains with 0 EV and 2 bars without excessive rpms. I’ve only tried that on rolling hills and lightly loaded with no cabin heat and HV did fine like yours. And the ICE was barely audible.
I’ve only had 2 HV trips with steep hills and both times were with >75% SOC. Both times the ICE only reved up to a pleasant lower-mid range hum kind of like my old gasmobile when downshifting to go up a hill. Not bad at all.
I haven’t had the courage to try that with 0 EV and 2 bars though. I think that plus passengers plus cabin heat would be risking the angry bees for a lot of us. I’d have to try it though for me to say with confidence what my Clarity would do. I can agree with your 100% letting the car decide but only up to 99.9% for me.
And I too ignore the dash MPG as it is so unreliable as to be useless. I just use odometer and gas receipts or kWh from my Charge Point.
Is this car great or what?
 
In HV, mine automatically goes into regen on the downhills even if the gear symbol is on. I don’t have to switch out of HV on hwy downhills to get regen. ??
 
insightman said:
Do you mean you disable HV to force your Clarity to switch to EV Drive mode?
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Yes that’s what I’ve done. For no other reason than allowing it to stay in EV mode for possible little short spurts of up hill or level ground that might come along on such long downhill stretches. And let me be clear I’m talking about decending mountains here. The Rockies, from 12,000 feet. Not just hills. Overall downgrades that might last 10 to 30 miles or more, with runaway truck ramps and the like. I’m certainly not pushing buttons for every hill in plain old rolling country. And as a Ken says, it might be pointless cuz if I left it in HV the engine probably would have just shut itself off anyway.
 
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KentuckyKen said:
@craze1cars, You’ve got a great Clarity if it will go up mountains with 0 EV and 2 bars without excessive rpms.
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You’ve misunderstood. I never said that it did it without high RPM. I said it got up those hills with no loss of power. Huge difference. By all means the engine sounded like it was hammering at 4,000 to 5,000 rpm the whole way depending on the steepness of the mountain grade. Same as any 4,000 lb 100 hp 4 cylinder car would be doing when it only has 70 altitude-induced horsepowers to work with.

When I said it had no loss of power, I meant the car could still maintain full highway speeds, and if I floored it it would still accelerate and had reasonable passing power. But heck yeah the engine was running nearly wide open as I’d expect it to under such a load.

When I’m hearing people complain of a sudden loss of power on their apparently defective cars, I am envisioning a scene where they’re cruising along at 60 mph and suddently the car slows to 30 mph or whatever speed, despite putting accelerator to the floor and engine screaming. Thus the safety complaints. If this is happening, the car is broke. Mine is not broke. It’s never done that.

But if careening up a mountain at highway speeds, able to maintain good speed and still accelerate, the car absolutely should be running very high RPM while doing so, and this is not a sign of a defect in the car nor a safety concern.
 
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craze1cars said:
You’ve misunderstood. I never said that it did it without high RPM. I said it got up those hills with no loss of power. Huge difference. By all means the engine sounded like it was hammering at 4,000 to 5,000 rpm the whole way depending on the steepness of the mountain grade. Same as any 4,000 lb 100 hp 4 cylinder car would be doing when it only has 70 altitude-induced horsepowers to work with.

When I said it had no loss of power, I meant the car could still maintain full highway speeds, and if I floored it it would still accelerate and had reasonable passing power. But heck yeah the engine was running nearly wide open as I’d expect it to under such a load.

When I’m hearing people complain of a sudden loss of power on their apparently defective cars, I am envisioning a scene where they’re cruising along at 60 mph and suddently the car slows to 30 mph or whatever speed, despite putting accelerator to the floor and engine screaming. Thus the safety complaints. If this is happening, the car is broke. Mine is not broke. It’s never done that.

But if careening up a mountain at highway speeds, able to maintain good speed and still accelerate, the car absolutely should be running very high RPM while doing so, and this is not a sign of a defect in the car nor a safety concern.
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Your post makes sense on the face of it. Why would Honda design a PHEV that under any condition would experience a dangerous or significant loss of power- short of simply running out of gas- or major component failure?

However there are a number of posts here that suggest that this does happen- and it is not clear that the dealer can diagnose and resolve the issue, or that Honda admits there is a defect. Some owners have concluded they must be super cautious not letting the battery drain down to a certain level, especially on moderate to steep climbs. Others have simply given up on the car.

Given that Safety comes first- what is your take on this situation? The above issues undoubtably do not show up in car reviews or dealer test drives. But they are not the kind of issues you want to show up after purchase.

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Lowell_Greenberg said:
Given that Safety comes first- what is your take on this situation?
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From extensive interactions in this forum, it seems like there are [some] who have experienced this dangerous loss of power for no apparent reason. I believe most of us do not have this problem. Having the loss of power scenario is dangerous and unacceptable.

If you have experienced this situation - PLEASE, report it to the NHTSA. It is s very simple form here:
https://www-odi.nhtsa.dot.gov/VehicleComplaint/

This is the only way that we can get the attention of Honda. Most of us have been lucky and do not seem to have this affliction. But if you do, reporting it will accumulate ammunition and Honda will have to start paying attention.

It is highly likely that there is a solution (likely a software update) that will ultimately correct this problem. It will not get corrected if nobody reports it however.
 
The vast majority of us are not experiencing the loss of power event. I’ve gone up two steep hills at 60-65 mph with the AC blasting and didn’t even get the angry bees. But I did have a hefty SOC and HV for me maintainins it.
Perhaps a work around until hopefully “the squeaky wheel gets the grease” for those affected would be to keep a significant SOC for HV trips.
 
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