Toyota Prius Forum banner
1 - 20 of 31 Posts

·
Registered
Joined
·
9 Posts
Discussion Starter · #1 ·
I live in Wisconsin and we just got our first snow. A really nasty icey mix. My mileage has dropped 4-5 mpg. I am sure this is because we don't plow the road very well and the rolling resistance is high.
I was just wondering what others are getting for mileage between summer and winter.

Just a note I know get to see the 37 degree light for about 5 months. Yipee Like we don't know it's cold out.

:p
 

·
Registered
Joined
·
1,661 Posts
Drop in mileage in cold is normal. I'm no science person, but do a search (on what term, I don't know) and you'll find someone on here talking about the density of air in summer and winter. No, I'm not kidding. Anyway, in rain or cold my mileage drops. In clear and dry and warm, mileage is more.

Also, it sounds like you might be a new Prius owner. Your mileage will improve in a few thousand miles, drop again with your first tire rotation, and then improve again. :)

Enjoy "flakey" for a few months! He'll be your dashboard companion. :)
 

·
Premium Member
Joined
·
640 Posts
I just got my worst mileage tankful average since the first one back in June when I was learning to drive a Prius (49.2 MPG). This tankful was 50.2 after averaging lower to mid 50s 'til now. It's inevitable as the temperature gets colder and the ICE takes longer to warm up. Other factors are in wet weather, whether cold or not, mileage suffers due to increased rolling resistance (as you mention) on wet roads. Related to that, mileage will take a hit when the defogger runs. And if you use snow tires, again, it affects mileage.
 

·
Registered
Joined
·
58 Posts
The engine has to keep running longer to keep the catalytic converter at an optimal temperature. Mileage suffers. It's a fact of Prius winter life... Lot's of green bar batteries.
 

·
Registered
Joined
·
95 Posts
As someone who has owned a '04 Prius since June 2004 here in Rochester, NY, I can tell you that mileage suffers greatly in winter. I think the main effect is due to the ICE running much more although it is clearly hard to separate out all of the effects.

When people here ask me about my mileage, I say 50 or low 50s in summer, dropping down to about 40 in the winter. In fact, on my worst tank of gas which coincided almost perfectly with the two most brutally cold weeks here last winter, I got ~35 mpg. Admittedly, my commute of ~15 minutes is a little on the short side so you might not see quite as much variation in mileage from season to season if your commute is longer and car had more time to warm up.

I also took to sometimes turning off the heater at stop lights in order to make the ICE turn off, although I got a lot of **** from my girlfriend for doing that when she was in the car!
 

·
Registered
Joined
·
298 Posts
jshore, I no longer live in the Rochester, NY area but my mileage dropped drastically here in Tennessee. We've had quite a spell of winter cold and my mileage has dropped from around 49 to 43 mpg. I guess it's just a sample of what is to come. *sigh* But it's still better than the 17.5 mpg I got with my Explorer.
 

·
Registered
Joined
·
46 Posts
Winter Gas Mileage

The type of driving you do in the winter will have a big impact on the gas mileage. If you have a long high speed daily commute, you won't see much change in mileage. If you have a short commute, mileage can drop significantly.

Be sure to check your tire pressure under ambient temperature conditions. If you only check your tire pressure when it is warm out, your tire pressure will be lower than you think.

The cold weather has me down to 58.6 mpg.
 

·
Registered
Joined
·
38 Posts
Re: Winter Gas Mileage

Chris Cording said:
The cold weather has me down to 58.6 mpg.
Holy crap! My mileage drops into the 30s when the temperature gets into the 30s (Fahrenheit). But then, I do a lot of city driving - lots of trips less than 20 minutes long.
 

·
Registered
Joined
·
2,348 Posts
I had one tank last winter in the 20's. It was nearly all below 0 (F) and mostly short hop driving as I was on vacation, and not commuting. Mostly last winter with mixed driving I got in the low 40's when it was cold.
 

·
Registered
Joined
·
46 Posts
Summer vs. Winter

In all fairness, I should admit that I put some effort in getting good gas mileage just for the fun of it. Tire pressure has a lot to do with it, and of course driving technique. My tire pressure is 56 front, 54 back (yes, I know the maximum recommended cold inflation pressure is 44 psi).

The weather warmed up a bit, and I'm back up to 61 mpg on this tank so far.

My wife gets low 50's on her Prius, with the same tire pressure.
 

·
Registered
Joined
·
420 Posts
Re: Winter Gas Mileage

Chris Cording said:
The type of driving you do in the winter will have a big impact on the gas mileage. If you have a long high speed daily commute, you won't see much change in mileage. If you have a short commute, mileage can drop significantly.
I probably shouldn't reply to this thread until I've had more experience in prolonged cold weather, but Chris' experience matches mine so far. As jshore has noted, the car takes longer to warm up in cold weather, and this is where a lot of the loss is. With temperatures in the 30s, our mpg were in the mid-40s after nearly 100 miles of in-town driving with our current tank - the worst mpg stretch we'd had since, well, since our first tank last winter. There were even instances of the car idling at stoplights, something I thought was a thing of the past! But a flying trip to Boulder - nearly 100 miles each way - brought the tank average up almost to 56, even though the temperatures were in the 20s to low 40s on the way up, and only briefly hit 50 on the way back.

There are other winter conditions that bring down mileage - such as snow and heater operation - but it seems the Prius, when warmed up, delivers pretty spectacular mileage on a dry road in cold weather. It will be interesting to repeat this trip with temperatures in the 'teens, though...
 

·
Registered
Joined
·
25 Posts
Sanny said:
Drop in mileage in cold is normal. I'm no science person, but do a search (on what term, I don't know) and you'll find someone on here talking about the density of air in summer and winter. No, I'm not kidding. Anyway, in rain or cold my mileage drops. In clear and dry and warm, mileage is more.
I would like to hear someone try to really explain the mileage drop. Warm up and idling to run the heater doesn't seem like enough to cause a 10 mpg drop unless you do lots of very short trips.

I know that aircraft performance improves in cold and/or dry air and degrades in hot and/or humid air. An aircraft ICE generates more power on cold/dry days than on hot/humid days. So why wouldn't the Prius ICE put out more power on cold days and be able to get the same acceleration with slightly less throttle?

Gary
 

·
Registered
Joined
·
7,161 Posts
kk6yb said:
Sanny said:
Drop in mileage in cold is normal. I'm no science person, but do a search (on what term, I don't know) and you'll find someone on here talking about the density of air in summer and winter. No, I'm not kidding. Anyway, in rain or cold my mileage drops. In clear and dry and warm, mileage is more.
I would like to hear someone try to really explain the mileage drop. Warm up and idling to run the heater doesn't seem like enough to cause a 10 mpg drop unless you do lots of very short trips.

I know that aircraft performance improves in cold and/or dry air and degrades in hot and/or humid air. An aircraft ICE generates more power on cold/dry days than on hot/humid days. So why wouldn't the Prius ICE put out more power on cold days and be able to get the same acceleration with slightly less throttle?

Gary
I don't know how aircrafts burn fuel, but a modern automobile ICE runs rich until it reaches proper operating temp, after which it runs at proper mix of fuel and air to obtain optimal burn. Colder weather would take longer to reach operating temp, and warming the cabin would make it take even longer. If during travel the ICE cools down too far, you may drop out of stage 4, sometimes you might even drop down to stage 1 depending on ambient temps and how long ICE was off.
 

·
Registered
Joined
·
151 Posts
kk6yb said:
I know that aircraft performance improves in cold and/or dry air and degrades in hot and/or humid air.
Part of the aircraft improvement is due to air density -- the wings work better.
 

·
Registered
Joined
·
25 Posts
MtnTraveler said:
kk6yb said:
I know that aircraft performance improves in cold and/or dry air and degrades in hot and/or humid air.
Part of the aircraft improvement is due to air density -- the wings work better.
Yes, I know but I'm talking about the piston engine (non-turbo) performance improvement because for a given volume of air in the cylinder the amount of oxygen is higher with colder (denser) air and dryer air (moisure displaces some of the O2).

Perhaps this (density altitude) doesn't apply with an EFI engine with VVT if the engine computer matches the amount of fuel injected into the cylinder to match the amount of O2 in the cylinder (there's probably enough sensors to do it and it's probably necessary to get the low emissions ratings). If it does run rich while warming up (but a rich mixture cools the cylinder delaying warmup!) as DanMan suggests then that probably is the culprit.

I was just looking for a scientific explanation for the cold weather mileage drop out of curiousity. I don't expect to see a mileage drop here in San Diego except from running the AC (it was in the 80's last week).

Gary
 

·
Registered
Joined
·
112 Posts
Cold air is denser, as has been said already. This
leads to two effects: 1> it is harder to push aside at
higher speeds, requiring more energy, and 2> the fuel injection system has to dump in more
fuel to maintain a stoichiometric burn of each cylinder
charge. That's why cold-air intake often results in greater
*power*, but reduced economy. You're burning more gas per
bang. Most modern cars route intake air from
somewhere ahead or above the radiator, i.e. *wanting* to take
in that cooler air and produce more engine power, but
it leads to great suckage in the Prius with a driver who cares
about mileage.
.
One fix is a warm-air intake, drawing from around the
exhaust manifold which is one of the hotter parts of the
engine's exterior. Old carbureted cars used to do that
with a small snorkel tube connected to a sort
of sheet-metal "stove" around the exhaust manifold.
It can be done on the Prius by rerouting some tubing
down under the first heat-shield; I've posted about
a web page I've got up about my own first-cut
experiment with this. So far it seems to be
working, although the engine still takes longer to
warm up in general if the cabin heat is on.
.
_H*
 

·
Registered
Joined
·
9 Posts
Winter Gas Mileage

I too live in Wisconsin and have seen the dreaded drop. I do not know where you live in Wisconsin but in the southeastern portion of the state we are stuck with reformulated gas due to being in an Ozone non-attainment area (thanks Chicago!). The winter blend of the gas seems to have the most major impact. It really sucks. We had a warmer than normal fall but I saw a drop anyway when the winter blend kicked in. I also used to see a drop in gas mileage on my Geo Prizm (3-5 MPG) when the winter blend use kicked in. Seems that the EPA is punishing us twice - once for higher price on reformulated gas for the privilege of living within 90 miles of Chi-town and then crappy gas mileage to boot resulting in using more energy resources.

I also noticed that on my trips to and from work (around 30 miles) the last 5 miutes of the trip I get a lot better mileage than the rest of the trip especially in winter so there is something to car being warmed up.

Ever notice that the trees in southern Wisconsin all bend to the south? Its because Illinois.....
 

·
Registered
Joined
·
2,348 Posts
hyperion said:
I hate to mention this but in two years I have never seen any notable drop in different seasons milage.
You think you got winter?!? Now we here, we got winter!! :wink:

Come visit in January. I'll show you the sights of Minnapolis and you can watch your average mileage plumit.
 
1 - 20 of 31 Posts
Top