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2019 Honda Insight EX (White Orchid Pearl)
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Just an update, in single digit temperatures, there is almost no difference from cold start with or without heat usage. Drive to work was 25.6 mpg, drive home without heat 28.2 mpg. My drive to work is usually 3-4 mpg less due to terrain.

PS I don't recommend not using heat at these temperatures, the drive home I was fighting with a windshield that was freezing over on the inside. I'm also sure that tire pressure was a factor, the last time I checked tire pressure it was ~45* ambient temperature.
We've not experienced single digits in Boston yet unless wind chill is factored in. Don't think wind chill affect cars. :p When it was under 20F earlier this week I needed the heater on. If I get on the highway I use the passive heater trick.

I'm trying to see if lowering the heater temp improves mpg(might test this later tonight). I usually set it to 65F but 60F seems comfortable enough for me at 36F outside temp. I managed to get 58.2mpg on a warm engine traveling 8 miles yesterday doing that. Previous trip was only a 1 mile drive so I've nothing to compare it to right now.
 

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We've not experienced single digits in Boston yet unless wind chill is factored in. Don't think wind chill affect cars. :p When it was under 20F earlier this week I needed the heater on. If I get on the highway I use the passive heater trick.

I'm trying to see if lowering the heater temp improves mpg(might test this later tonight). I usually set it to 65F but 60F seems comfortable enough for me at 36F outside temp. I managed to get 58.2mpg on a warm engine traveling 8 miles yesterday doing that. Previous trip was only a 1 mile drive so I've nothing to compare it to right now.
I generally do not turn it above 65 unless trying to burst defrost when engine is warmed. Usually I keep it at 62*, I know ~3-4 degrees will reduce the fan load, so I assume that each fan load is a better "economical heat set point"
 

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Discussion Starter #63
I haven't looked through the entire thread, but I experimented with this on one of our few cold days here in FL. I put a digital food thermometer in the vent, set the heat to high and turned it off - then directed the heat to the windshield and front vents. It was interesting to see that the readings actually got upwards to around 160-162 when the engine was running. When the engine went to EV mode, the temp coming out would drop very quickly (~50-60 degrees). Later I turned the system on and reset the temperature to around 85 - and it stayed pretty constant, only cooling off slightly if I managed to get EV mode to stay on for a longer amount of time. If you don't want to cook - you can turn down the heat and it will regulate it some.
 

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Is <20*F the threshold dependent on length of drive? I was kind of thinking the opposite... that cabin heat would be more helpful/impactful on battery pack if temperatures are below freezing, since the battery charges/discharges more slowly at low temps.
Yes, the longer the drive, the more normalized your gas mileage will become.

During a cold day, we decided to drive to Chicopee Ma. Used cabin heat for ~15 minutes, switched to passive heating, and saw almost "summer time" mileage when we reached our destination. (about 3 mpg less)

Compared to my daily commute where I can see numbers as low as 25 mpg compared to 48-52mpg. Cabin heat provides a small bump towards the end of my commute, and below 20*F hasn't seemed to reduce mpg. Compared to 30-40*F where I notice a drop in mileage.

We are out of Super cold days for now (single digits), but I can safely attest that the gas mileage on a short commute (under 12 miles) is negligibly affected by cabin heat usage, and I suspect that if beyond 10-15 miles into a commute and switching to passive heating; I'd expect to see much more normalized mpg numbers.

For an interesting comparison:

@12*F my commute home was ~29mpg
@34*F my commute home was ~68mpg

Both were with climate control off.
 

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Today I was idling with the heat on, and I found out something that maybe will be of no surprise to some of you but I thought it was interesting.

The heater was set at 70°F with a constant fan speed set. When turning the knob down to 68°F, the engine shut off. So far so good. But then every degree above 70°F all the way to "Hi" revved the engine faster! So I was literally controlling the RPM of the engine with the temp knob.

It's surprising to me because I would have thought just the engine idling would be enough to reach at least cabin temperatures in the 70s. But apparently not. Or Honda really wants it to happen as fast as possible.
I was in heavy traffic last night so passive heating wasn't cutting it to keep the windows fog-free. I had to turn the climate control on to clear the windshield. The climate control was on 'HI' (to maximize passive heat) so started the gas engine with a much louder rev/jolt than I had ever recalled. But the window certainly cleared very fast (seconds).

So I think I replicated what you described, and must have put the car into immediate high RPM when I turned on the climate control. It doesn't seem like a 'healthy' condition to immediately put the engine in when first started, so I'll plan to turn the temperature control down if/when I need so use while in slow/idle speeds next time...
It gets me thinking... Do we actually need the heater on Hi for passive heating? What if the hot air duct is already fully open at 70° and above that it's just a matter of engine rpm?
 

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It gets me thinking... Do we actually need the heater on Hi for passive heating? What if the hot air duct is already fully open at 70° and above that it's just a matter of engine rpm?
No, you don't. Actually, keeping it at 'hi' in passive mode made it TOO warm for me a couple times. It all depends how cold it is outside and how fast you're moving.
 

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It gets me thinking... Do we actually need the heater on Hi for passive heating? What if the hot air duct is already fully open at 70° and above that it's just a matter of engine rpm?
No, you don't. Actually, keeping it at 'hi' in passive mode made it TOO warm for me a couple times. It all depends how cold it is outside and how fast you're moving.
I meant IF I wanted to have the maximum throughput, is Hi any different than 70°F.
 

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I meant IF I wanted to have the maximum throughput, is Hi any different than 70°F.
I suspect so, but it's not something I can test due to short drive and stop-and-go commute. (My windows are pretty fogged up when I arrive to destination, but I suck it up for the mpg help.)

Someone with a longer drive and consistent speed would be better to test/compare what the effect of HI is versus 70F. Might be best to test on two entirely separate drives to have the same starting temperature in cabin.
 

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Today I decided to turn the heat on because I didn't spend 30k to be miserable...

Anyways, the same trip that would return 43mpg in the same weather returned 32mpg with the heater at 68F... Outside: 20F, 11mi commute, slightly uphill, mostly highway, 65mph, no remote start.

So yeah, not great at all but I knew it.
 

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Today I decided to turn the heat on because I didn't spend 30k to be miserable...

Anyways, the same trip that would return 43mpg in the same weather returned 32mpg with the heater at 68F... Outside: 20F, 11mi commute, slightly uphill, mostly highway, 65mph, no remote start.

So yeah, not great at all but I knew it.
I keep mittens in the car for this exact reason. I uses to use passive heating on my 50-mile commute. It took a good 20 minutes before things warm up.

I tried active heat the past few drives. I've found setting it at 65 degrees works best. I can hit EV mode after 3-5 minutes and be comfy for the remainder of the drive. This seems to be the best split to get the interior and HV battery at a decent temp to gain more EV effeciency. I now suffer with the mittens until I know the car has a warm engine, then I switch on the heat to 65. I've been pulling mid-60MPGs to work in 35 degree temps so far this week where my summer average was 70MPG. That's less of a drop than the expected 20% most are seeing.
 

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FWIW, I have been starting with a cabin temp set to 58 which is hit very quickly (garaged car). As the drive progresses, I kick the temp number up a degree every few minutes. The ICE never prevents EV mode with this method. I stop at 65 degrees.
Do you start with fan/system on, or passive set at 58F? And when you adjust the temperature number, you turn the fan/system on to adjust, yes?
 

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Do you start with fan/system on, or passive set at 58F? And when you adjust the temperature number, you turn the fan/system on to adjust, yes?
Active. I no longer use passive as, once the interior hits the requested temp, the normal ICE engagement seems to be enough to keep up. Only over 65 have I ever been denied EV due to "Cabin Being Heated". The secret appears to be raising the cabin heat by a degree or two every few minutes until it is at 65.

I start garaged, so the initial at 58 doesn't take much. Your mileage may vary (see what I did there?).
 

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Active. I no longer use passive as, once the interior hits the requested temp, the normal ICE engagement seems to be enough to keep up. Only over 65 have I ever been denied EV due to "Cabin Being Heated". The secret appears to be raising the cabin heat by a degree or two every few minutes until it is at 65.

I start garaged, so the initial at 58 doesn't take much. Your mileage may vary (see what I did there?).
Thanks for the tip.

I've been doing short bursts of heat in manual operation, with temp. set at "Hi" or down to 80 on later parts of longer drives (the air it blows is not so hot) or just do passive when cabin is warm.
Interesting idea you have for automatic operation, will give it a try! Thx
 

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Sad day for me yesterday... it was the first drive of the season where the ICE started immediately as I powered on the car. :(

Garage temp was ~65F but ambient temp was ~57F and (manual) climate control was set to 62F. With the cabin temp set lower than garage temp, I thought the car would start in EV mode (as it had done all summer). But the weather has definitely cooled. I quickly cranked the temperature setting to HI and turned off the fan to prevent the ICE from continuing to run (after initial engine warm up).

Net, it's that time already, and yesterday was my first use of 'passive heating' for the upcoming season... lower mpg ahead. Plus gas stations are in the process of transitioning to winter gas blend (which started ~9/15) and I filled up on this winter blend, as my first refueling after fuel pump recall repair.
 

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Interesting. I should probably read things and learn how to use my car. Been playing with this and other than making my hazard switch constantly pop out of the dash it has worked pretty well with the outside air temperature (OAT) these past few trips being between 40-60.
 
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