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Damn! Just another reason to hate winter.

I have been noticing that the mpg of my I2 drops along with ambient temperatures. I bought my I2 EX w/Navi in June 2010. As the car continued through a "break-in" period the mileage continue to increase...at least until the weather began dropping. To illustrate, here are examples of my mileage.

Jun 24 - 41.06 mpg (initial fill)
Jul 26 - 42.31
Aug 16 - 43.23
Sep 15 - 45.56
Oct 07 - 44.18
Nov 24 - 41.92
Dec 20 - 40.77
Jan 26 - 38.81

In the interest of brevity I only listed every other fill but you can still see the pattern. I should point out that these are calculated mileage figures--not MID values (MID over estimates by 2 - 3 mpg).

Also note that my driving habits vary by season. The majority of my driving May through September is comprised of trips of 20-40 miles, mostly expressway or secondary highways. The remaining months are made up of short trips, 10 miles or less, almost all city driving. That, coupled with winter fuel blends and the fact that the I2 seldom auto-stops when the temperatures are low, all add up to the observed mileage drop.

For the record, I am not disappointed with my I2. On the contrary I really like the car. It is fun to drive and the overall mileage, so far (42.33), is better than any car I have ever owned. My wife's Scion xD only gets about 31 mpg--but she only drives around 2,000 miles per year so who cares!
 

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Our EX has about 21.5k miles on it. The lifetime average is about 44.6 mpg.

We live in Wisconsin, park outside, and see about an 8-10 mpg difference between seasons. In the spring and fall we average a touch under 50 mpg. In the heat of the summer with AC on we average about 46-47 mpg. In the winter (and it has been COLD) we average about 40-42 mpg.

It is a mild irritation to see figures drop in the winter but I expected it and am not disappointed.


In the winter I do get an intermittent squeak coming from around the glove box. That irritates me more than the mileage.
 

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Yeah, 15mpg drop here and thats just using the heat on 70 degrees. The more heat you use the lower it goes. :(
 

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We get a double hit in winter because it's always windier too.

Try a -30C cold start, 550 lbs of passengers, heat and defrost on full, and immediately heading out onto the highway at 100kmh into a 60kmh north wind. Mileage dips below 30mpg (US). My average this winter is 36mpg (US).
 

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This winter in New England has hit my mileage hard. Between the Snow and sub-zero morning, I am on my way to my worst tank ever, looking like maybe 34 - 35 mpg actual showing close to 37 on the MID. My mileage has been on a steady decline since November. Looking forward to warmer drier weather and a return to mid 40mpg.
 

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Man, here I was thinking I had dinged my fuel lines (didn't help that the drop in mpg happened right after I bottomed-out).

3 degrees this morning. Getting 38.3 MPG for this tank. I hate coasting, staring at my MID, waiting for it to tick up .1.

Cobb, I thought I was overthinking things, but you say the heat temp will affect it? I usually run at 80 until I get hot (which doesn't happen much these days by the time I get out again), but you recommend dropping to 70 or so?
 

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Yeah, use of the heater lowers the mpg, lessens the likely hood of going into the brief moments of EV only and even defueling of the engine coasting. So, your motor is likely always burning fuel.

Yeah, I bundle up and set the heat to around 70. One reason I like my geo metro. It produces hot heat and can maintain around 50mpg. :)

If VA Beach is like Chicago, I got 34 in city, 65 on the way down one day I was there for 300 miles of driving. Not bad, my previous car a 09 scion xb got 19mpg, wher eas it normally gets 30.
 

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I'm thinking the heat doesn't take away mpg, but windshield defrosting does since it automatically turns on A/C.
The defroster definitely affects MPG significantly. However any drain on the electrical system, to include the blower, will have an effect on MPG. However, IMO, I think using the heat without the defroster, has a negligible impact on fuel economy. The way I see it,(and I may be wrong)the heat is a byproduct of the ICE and all you're doing by using it is pumping a little of it into the cabin.


Winter mileage, in all cars, sucks for many reasons(see link below). IMO, not using the heat will not help much.

All that being said, I would limit the use of the defroster as much as possible.


http://www.metrompg.com/posts/winter-mpg.htm
 

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Your ICE theory is correct...in theory.

OTOH, the ideal conditions for the engine to get the best mileage comes when the engine is warmed up to designed operating temperature. This is when all the parts and the oil are at the same optimal temperature.

It is possible that running the heater will act as a radiator and wick away the heat that the engine needs. You would need a ScanGauge or something like that to watch your temperatures. If it can maintain about 175 degrees, that's probably fine. If it gets much less than that, there are probably parts of the engine that aren't heating up enough and the ICE is inefficient.

I don't know for sure if the Insight fits this situation. If it was running too cool, I would suggest one of the grill blocking techniques discussed on this forum. There are a lot of factors such as outside air temp, how far you drive, and how you drive to consider.
 

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Your ICE theory is correct...in theory.

OTOH, the ideal conditions for the engine to get the best mileage comes when the engine is warmed up to designed operating temperature. This is when all the parts and the oil are at the same optimal temperature.

It is possible that running the heater will act as a radiator and wick away the heat that the engine needs. You would need a ScanGauge or something like that to watch your temperatures. If it can maintain about 175 degrees, that's probably fine. If it gets much less than that, there are probably parts of the engine that aren't heating up enough and the ICE is inefficient.

I don't know for sure if the Insight fits this situation. If it was running too cool, I would suggest one of the grill blocking techniques discussed on this forum. There are a lot of factors such as outside air temp, how far you drive, and how you drive to consider.
I don't really know how any of it works, but just for kicks I've been not really heating my car much at all as Cobb suggests. It's a bit of a pain when it's cold, but realistically the heater takes a good amount of time to pick up and once it does I usually drop it to 68 or so anyways. Now I just leave it on 68-63 and wait for the car to heat up.

Having done this I feel like accelerating hard before the car warms up is taking less of a toll on my mpg. But of course, I could be imagining things, and I am want to do.
 

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You are right. The Insight could benefit from a cooler thermostat. I see from my scanguage it hovers around 154 for stop n go driving and 177 for highway. My attempts to completely block the lower grill during the summer with no ac hurt vs helped mpg. I started to hack up my block and find leaving a 4x4 inch opening to work best. I also have foam from a water noodle inserted on 3 of the 4 sides so air has to pass through both the condensor and radiator vs escaping around the condensor. I wasnt able to repeat my 69.6 mpg unless I had the foam on all 3 sides.

Currently I have hte foam in place and all but an inch down the middle of the grill glocked off. I tried inserting a piec eof cardboard per the i1 owners, but it hurt vs helped it. I removed it and it went up. WOW.....

Jus the other day it was 30 out, I was wearing a jacket and had the hvac set to low and off. I was hovering between 55.4 and 55.6 mpg. I turned the dial on vent to 72 degrees on the lowest fan setting. Wow, a mile latter I clicked pass 56mpg. I turned the heater to high, it went back down. I hit the off buttom, no effect. I turned it back on, set it to 68, then turned it back off. BOOM, got my 56mpg back.

Seems this engine or the iDS is temperature sensitive.
 

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Humidity & climate control

It's not the heater that hits fuel consumption, it's humidity. Heating the cabin up the climate control needs to run the AC in order to dehumidify the air. That said the payoff is that the inside glass doesn't "fog up" with condensation as it will the the AC off in winter. It's worth noting that, unsurprisingly on my own in the car the climate control doesn't have to dehumidify the car as often as it does with my GF next to me as we breathe out a surprising amount of warmed moisture when the air is damp/humid.

Some people question why a car that's ostensibly focused of fuel efficiency has climate control at all but the answer is pretty simple; efficiency oriented climate control both prevents over use of the fans & AC but also creates a more relaxed, comfortable driving environment, which is conducive to a more relaxed and economical driving style.
If you draw on your own experiences you know that drivers who are hot, cold and/or sat in a humid car are often PO'd at being there and tend to drive more aggressively because they just want to get where they're going and get out. Making the driving environment a nice place to be encourages drivers to sit back and relax, even in traffic and that encourages people to take it easy rather than ramming the accelerator in to the carpet at every opportunity, which can make a big difference to fuel economy. :)

Setting the climate control to a comfortable temperature and leaving it on auto may seem counterintuitive but the impact on driving style can be dramatic. In winter we tend to leave the our car's climate control on 20℃ (68℉), although on longer journeys we tend to turn it down to 19℃ (66.2℉) after about 30 minutes, and in summer we tend to leave it on 16℃ (60.8℉), then just leave it to it's own devices. As you can probably tell we're used to a cooler(ish) climate here in the midlands of England. We've only had our I2 since December, so I can't speak to the impact of winter on economy just yet. :)
 

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This winter in New England has hit my mileage hard. Between the Snow and sub-zero morning, I am on my way to my worst tank ever, looking like maybe 34 - 35 mpg actual showing close to 37 on the MID. My mileage has been on a steady decline since November. Looking forward to warmer drier weather and a return to mid 40mpg.
Yeah, this winter is killing mine too. I'm pretty cold tolerant, and in the mornings will a lot of times not use the heat since the car has been in a garage. However, even though the screen is off, sometimes I can feel hot air blowing out of the vents. My drive in to work during warmer months can reach almost 60 mpg, but in the winter, even with the heat off, I get nowhere near that. Probably max 45.
 

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Thats why I said I set the knob to lo, otherwise it wtill still allow air through the heater core if its set for anything more than lo and even in the off position.

However, even though the screen is off, sometimes I can feel hot air blowing out of the vents.
nliwilson, it only mixes ac with the air if the auto feature is used or ac is turned on in manual mode. Like said, if its humid, this reduction will allow autostop, so it may break even if used.

When I have fog I just hit the defroster button when coasting or down a grade. When I start going up again I turn it off.

You set it lower for the summer vs winter? I used to use78 or higher in the summer. Many cases I just use the blower and outside air and click ac when I am going down a grade. The most efficient way for summer is to set it on manual, lo, recirculate and just use the blower speed toregular the temp in the cabin.
 

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nliwilson, it only mixes ac with the air if the auto feature is used or ac is turned on in manual mode. Like said, if its humid, this reduction will allow autostop, so it may break even if used.

When I have fog I just hit the defroster button when coasting or down a grade. When I start going up again I turn it off.
I used to use78 or higher in the summer. Many cases I just use the blower and outside air and click ac when I am going down a grade. The most efficient way for summer is to set it on manual, lo, recirculate and just use the blower speed toregular the temp in the cabin.
I see what you're saying and I admire your commitment but part of the design brief with hybrids is that you should be able to use it just like any conventional car, without the need to think about what the climate control is doing for example.
The "average driver" simply doesn't want to keep fiddling with heater controls and some will question where your concentration is, although I appreciate that you have a routine with it. As I said, the reason the car has climate control at all is to keep the cabin not just comfortable but a nice place to be, so you sit back and relax and for me personally constantly adjusting controls isn't relaxing! :)
Given the energy used by the demister/defroster I'd be interested to know how much difference making continual manual adjustments makes in terms of fuel consumption and how foggy your screen can get before you reach a downward incline?

You set it lower for the summer vs winter?
This is England man, our climate doesn't do consistent temperatures and neither do we! LOL! :D
Seriously though that's simply what my girlfriend and I both find comfortable. I honestly think a big part of it is that we have so few of what we would call "hot" days that we don't deal with them well. Our idea of a blazing hot summers day is around 33℃/91.4℉. :)
 

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You CAN drive this hybrid like any other car. You can set the climate controls where you like them.

The discussion was that mileage drops in the winter, and possible ways to gain a little of that back.
 

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You CAN drive this hybrid like any other car. You can set the climate controls where you like them.

The discussion was that mileage drops in the winter, and possible ways to gain a little of that back.
I'm following this discussion with interest because I've only had my Insight since December, so have only driven in winter, and am not getting the milage I'd expect (46.2 mpg) given that I'm both driving economically and using the eco instrumentation to guide me, ensuring I drive economically.

As I said in my first post, dehumidification will hit milage in winter, but I'm also pointing out that being relaxed when driving can have a dramatic impact on fuel consumption and for me personally if I'm constantly altering the heater controls I'm going to be less relaxed, so I'd expect my milage to be worce over all, not better. That's why I asked Cobb if he was seeing a difference with his chosen method of managing the dehumidification issue? If he is then it's a good tip for everyone, including me, but if it's not making a palpable difference, it's only making a very small difference or it's creating a new problem by allowing the screen to get excessively foggy then I won't bother. :)

Don't get pissy at me for answering one question, asking others that are entirely on topic and pointing out an issue most people don't take in to account, yet which can potentially be the biggest factor in poor fuel consumption!? That's not in any way, shape or form constructive and going down that road only invokes Godwin's law! :mad:
 

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I find the auto temp setting works best when you have paseengers. Hey, its set to 68 degrees, LOL.

I dont have that many problems with the windshield fogging, mainly the side windows. Either use of the ac or defroster takes a hit in the mpg. For some odd reason the rear windows will fog right over, on those days and it slike once a month I do set it to auto for a few, then turn it back to manual mode.

 

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I find the auto temp setting works best when you have paseengers. Hey, its set to 68 degrees, LOL.
LOL! That's OK then, I always have it on auto with passengers for their comfort, it's a nice surprise to find it's the right thing to do as well! ;D

I dont have that many problems with the windshield fogging, mainly the side windows. Either use of the ac or defroster takes a hit in the mpg. For some odd reason the rear windows will fog right over, on those days and it slike once a month I do set it to auto for a few, then turn it back to manual mode.
The kind of fogging you've shown in your photo there is nothing, I can live with that, but the rear side windows fogging over can be a pain on motorway driving? I'll try experimenting with your method of minimising AC use and see how it compares to the eco-assist computer's way of managing it and let you know if it makes a difference for me, baring in mind that this is a damp country and I expect my windows/front screen to fog over more than that in our local climate. So if I don't post the results in a couple of days you'll have to assume they fogged over completely and I crashed! LOL! ;)
 
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