As your IAT sensor detects colder air, it makes the mixture richer. As the temp drops, grease and oil get thicker and tires don't roll as well. Add that to your denser air and fuel that's blended for winter (which decreases mileage) and it all adds up to a problem. Now if you let your vehicle idle more to warm it up and you don't get EV mode b/c your battery is cold, you're really going to notice it.

 

I'd like to second the post from Billyk and (unfortunately, because I know where it will lead) go against what Willard has said.

I have a drive that I do occasionally for work that is over 150 miles round trip of rural highway that I can (until yesterday) ALWAYS count on above 40MPG for the trip. Yesterday, the temperature was around 27-36 degrees using the on-board thermostat and confirmed by roadside signs that offer time/temp. During this drive, I only did 33MPG. I expect (like Billy) that this is due to the cold, denser air. I did check the tire pressures and they were where I always run them. During this long of a drive the various lubricants would have plenty time to warm up. Now, this is also where I disagree with Willard since I saw plenty of regen and full battery charge on the few stop lights and speed reduced zones along the way. I also had plenty assist from the battery the one time I did have to pass a logging truck that was spewing chips. (I didn't need to use the ABS and I don't have a 4wd so I can't comment on those item's functionality).

I know there's a thread regarding someone talking about a warm air intake. When it's cold out (yes, I know, 27-36 isn't REALLY cold ), I can't help but think this would be worth a shot.

 

40MPG down to 33MPG....~17% FE loss...due to cold, denser air....

Yes, COLD/DENSE air will generally result in running with an enriched mixture, especially until everything is warmed up to operational temperature. But thereafter.......

But 17%.....???

And the patent only calls for a reduction in regen for "lift-throttle", coastdown events, not if actual braking is involved.

Full battery charge...of course, if regen can't be used adequately then the firmware will use the ICE for "makeup".

 

I wonder if the blend of your fuel changed or maybe you filled at a different station?

 

Nope... same station as always and we've been E10 for a long time. I'm on the SE coastline so there's no winter gas blend as far as I'm aware. Like I said in my post, all thing were equal as best as I had control over. There appeared to be no indication of wind (judging by the trees and other indicators and it was a round trip) and I'm positive that over the last 30,000 miles my driving style hasn't changed that much (especially on this circuit). I wasn't running the heater very much once I reached a comfortable cabin temp (this happened in the first 10 miles or so) and I had several layers of cloths and a jacket.

Willard, almost of my slow/stops on this trip are done by using LGA. Since I know this route and traffic is very light, I get to ease up to lights and speed zones. There are only a handful of those in any case. As for steady state driving there would be no regen in any case, but there would be assist (as needed). I did pass one log truck that was spewing chips everywhere. There was plenty assist on this one time event.

It's trips like this that I wish I had a scanguage to gather more info.

 

As you may have noted, read, there was a previous post wherein the owner noticed that the ICE was consistently running in higher RPM ranges in cold climates. My explanation, "theory" was/is that was the case since the ICE had to be used for recharging the battery since regen was incapable due to the low OAT.

I have noticed on the Prius that on long hwy drives when there is not regen opportunity the control system will let the SOC deplete down to about 1/2 and then decide it must make use of FUEL for recharging. If I remember well/correctly, this "cycle" ocurred about 3 or 4 times on the trip to Portland from Seattle on I5.

Apparently the early Prius firmware is designed to "wait" as long as is reasonable for a regen opportunity to arise and if that doesn't happen then teh ICE is used. In your case not far into your COLD drive the ECU would "know" that no regen was likely to become available so it might use the ICE continuously.

Since you didn't make mention of noting anything of this nature I assume you didn't pay attention to ICE RPM vs roadspeed...

But its probably worth asking...

 

The Escape and Prius have different software, hardware and "firmware". Ignore Willard's statements.

 

COOL! Thanks WWest I new my FEH was smart but.... It can see the future too!!!

 

I don't own a FEH either. Is it alright if I post here or is FEH ownership a requirement to post in this section?

While the cold does effect certain hybrid functions (like auto-stop), non-hybrid vehicles suffer from poor mileage in the cold just like hybrids.

The decrease in MPG is caused by:

1) Non moving warm up time.

2) Engines all run rich till they warm up, thus consuming more fuel. In the Summer my car is warmed up within the first mile. In the Winter it can take up to 8 or 9 miles for the car to warm up to full operating temperature.

3) Lube gets stiffer and take more energy to overcome friction.

4) If you don't put more air in your tires PV=nRT will cause your tires to be under inflated in the Winter adding to rolling resistance.

5) If there is snow on the road this will increase rolling resistance (a lot) as well.

 

What do you drive? You mention auto-stop and that is a term common to "other" hybrid drivers but rarely mentioned by FEH owners. I'm assuming you are not located in a northern state where severe winter conditions can exist. Where are you located?