2010 Prius MPG in cold weather?

I am getting mpg's in the lower 50's. I live in southern Wisconsin though and I have a heated garage that keeps my starting engine temps around 50 degrees. I also try to drive between 50 and 60 mph as much as possible which I hear improves mileage. I see higher mpg's when I drive 50 instead of 60 but it could just be that my car is warmer too.
So I'm not sure if a block heater would help or just driving slower because last year I got mpg's in the 40's and I wasn't able to warm my car up at all. I have also heard that mpg's improve after a certain number of miles. So it could be that too.
I also use half inch foam pipe in my grill which has helped a lot. If you go to walmart or any hardware store you can get it really cheap. I block 75 % of the bottom grill and 50% of the top grill when outside temp is below 40 degrees and I see fuel mileage stay around 50 mpg until outside temps get well below freezing.
Here are some guidelines I have used from the guys that own the scangauge.
Celsius/ Farenheit/ upper blocking%/ Lower blocking %
below 5/ below 41/ 100/ 50
5-18/ 41-64/ 75/ 50
18-30/ 64-86/ 75/ 0
above 30/ above 86/ 50/ 0

Ken@Japan ​

Plugging in…
Do try a timer with a 3 hour pre-heat when the ambient around your car is less than 50F. At an ambient around your car of less than 20F plug in as long as you can. Using these guidelines I've seen starting engine temps from 60-80F above ambient.

 

You should read the sticky thread:

http://priuschat.com/forums/gen-iii...y/99492-why-mileage-gets-worse-in-winter.html

Plus short commutes under 10miles can really kill mpg regardless if it is cold or not.

 

The Prius is more sensative to MPG in winter than any other vehicle I have owned and I have been driving since 1966.

My 2003 VW Jetta Wagon model GL TDI (Turbo Diesel) 5- speed manual transmission gets 52-54 mpg consistently in summer and 50-52 consistently in winter.

Now to our Prius in summer in the mid 50's mpg range; Now in the winter mid 40's. A noticable difference. In fact last fillup was only 46.78 mpg, 2 months ago it would have been at least 54 mpg.

So lets review, my Jetta gets a 2-3 mpg loss in winter, the Prius 6-9 mpg loss.

I am not complaining as diesel fuel is at least .30 - 50 cents more a gallon than reg gas. I am sure other Prius owners have also noticed this.

alfon

 

Last year's graph of my driving experience provides a good idea what to expect in the northern extremes, with a 16.5 mile commute...

 

Or, better yet, skip straight to http://priuschat.com/forums/gen-iii...mileage-gets-worse-in-winter.html#post1411488.

 

how cold is it? it has been very mild here. i'm still getting 60mpg. probably translates to 65 in the gen III.

 

Once temps get below freezing, it's hard to get even mid 40s, unless perhaps you are a pro hyper-miler and have no short trips. We usually get 55mpg+ in the summer, but manage only around 40mpg once it drops below 30F. We have a lot of trips under 10 miles, so it's definitely not ideal, but still better than the Subaru Outback it replaced that got half that;-) As for getting better mpgs, all the usual things you read about here of course. In particular, tire pressures drop in the cold, so give them a fill, perhaps even to above the rated pressure.

Also, having a soft foot is good, but to maximize hybrid mileage you want to maximize the time you drive with the internal combustion engine off. That means coasting or gliding as much as possible, rather than keeping a steady pressure to maintain your speed like you would in a typical car. This alone seems to be a greater than 10% improvement for us in warm weather, even on short trips. Problem is that in the winter, it takes so long to warm the car up that you barely get to the point where the internal combustion engine shuts down on a short trip. So, you not only lose any most of the benefit of coasting and gliding, but also have loss from the other temperature related effects on the system.

Yeah, it sucks. On a percentage basis, you do lose a lot more miles per gallon in the winter than a typical car. It helps a little to keep in mind that although you are only getting 40mpg, you're still saving a lot of fuel even compared to something fuel-efficient like a Toyota Yaris in the same conditions.

 

Funny .... I've never experienced the big dips being talked about. I expected my MPG's to go way up in the spring and summer (from about 48) and they never did. I've averaged right at 48 MPG calculated for the first 20K miles, and have never experienced the big winter drop. I did get a quite substantial summer drop (to around 46) with considerable AC use. Best I've gotten is 57.6, and the worst is about 45.

We get real winter here as well in NE PA.

I'm thankful I never really get the big hit. I don't hypermile at all ... just drive conservatively all the time.

Regarding the engine taking a long time to warm up ... mine comes up to 103 in about 1/2 mile (when the heater fan comes on) and is in the 150's by about a mile of flat driving. Fastest warming up car I've ever owned ... I love it !

REV

 

I am down to about 41 for this month due to mostly 10-12 mi commutes in 40F temps. I usually avg about 44 overall.

 

Between Nov 17 2011 to Dec 16 2011, the mean temperature for the state of Wisconsin has been between 20F to 40F with most of the state hovering 30F degrees. Precipation has been light between 0.5 to 2.5 inches. [1]

Assuming you are not using snow tires (or using chains) - check your tire pressure, set your tire pressure to atleast 35psi front and 33 psi rear (toyota recommend specs) up to the maximum sidewall tire pressure setting. Assuming your Prius is using stock Toyota OEM Yokohama Avid S33 tires which has a maximum sidewall tire pressure of 44 psi, this translates to 44 psi front and 42 psi rear. Technically, the higher tire pressures reduces the Prius's tire's rolling resistance. The higher tire pressure makes the Prius coast/glide better (move via momentum rather than by energy exterted by the gas engine or the electric motor) when on a dry smooth road. It also makes the Prius more fuel efficient when the gas engine is burning fuel too. I've set my tire pressure to 50 psi front, 48 psi rear -- however, the advantage of going over the maximum sidewall pressure is minor unless one is hypermiling - my higher tire pressures is part of a two year hypermiling experiment I am doing.

If you are using a shorter route which has unfinished, rough, or bumpy roads try switching to a longer route which has finished, smooth roads - your MPGs will improve dramatically.

At your current temperature, grill blocking is safe but grill blocking tends to provide the best results in stop and go traffic situations. In superhighway driving scenarios, grill blocking fuel efficiency advantages fade after the first 60 minutes of driving. I am currently grill blocking ( 100% top 100% bottom) however most of my driving is done in stop-n-go congested city/suburb roadways.

Wisconsin is a big state, if you are driving on superhighways with the speed limit of 75 or 70 mph and you are driving between 70 mph to 80 mph - then 40 mpg is a reasonable expectation since the EPA MPG rating test uses lower sustained speeds to compute fuel efficiency. You would have to drive at a lower highway speed to something betwen 50 to 60 mph before seeing something closer to 50 mpg range.

At your current temperature, Toyota's 400W engine block heater (EBH) is useful (if you don't have a heated garage but have acces to a outside 120VAC outlet. I've read it may take from 30 minutes to 120 minutes for it to sufficiently warm up your car and it will cost you electricity too. Reportedly the EBH will last from three to six years (san accidental cord breakages) and cost about $60. The major cost is installation and whether your service tech has any installation experience. There is a official toyota and an unofficial hypermiler's EBH installation guide for 3rd gen EBH via the internet. I am planning to install one in my Prius...unfortunately, even the toyota dealerships in my neck of the woods have zero experience with installing an EBHs

A soft foot for the Prius means keeping your HSI display on the left side of the center at all times. This can be problematic if not difficult to do in the real world. In the real world, a much easier technique to achieve higher fuel efficiency from the Prius is to synchronize accelerations when the Prius is going downhill and avoid accelerations when the Prius is going uphill. In hypermiling circles, this is call DWL or driving with load.

If you are driving less than 30 minutes per trip or less than 6 miles per trip - your lower MPG is mainly due to the warmup penalty that the Prius has (to achieve its Ultra low emissions level). You can mitigate this penalty by using grill blocking and/or an EBH. You can also reduce this FE hit by driving several smaller trips in rapid succession (with stop overs that are less than 10 minutes each) with the longest trip first and the shortest trip last. Each succeeding trip benefiting from the previous trip which has warmed engine for the next trip. Also parking your Prius in the afternoon sun can help keep it slightly warmer too...

At the temperatures you are driving in - you are probably using the heater and the defroster alot too and there is a big hit in fuel efficiency for using them as well. The FE tip I've read/seen wrt to the heater is to *pulse* the heater on hi then turn it off until it gets so cold you need to use it again. Manually remove the ice/frost from your windows with a window ice scraper before using your windshield defroster can also help too.


hope this helps

Walter Lee
(aka "HyperDrive 1" mileage log posted in cleanmpg.com)
2010 Toyota Prius III, Blue Ribbon/Dark Grey, oem floormats
Yokohama Avid S33D (50/48 psi)
100% grill blocking
ScangaugeII(Fwt/AVG, SoC, GPH, RPM/MPG)
Odeometer +18000, overall MPG=61 mpg
best tank 70 mpg, worst tank 52 mpg, last tank 63 mpg
Dc/MD/VA metro area

[1]
http://www.aos.wisc.edu/~sco/mrcc_images/tmean-30days.png
http://www.aos.wisc.edu/~sco/mrcc_images/prcp-30days.png

 

Another reason for the big drop in mpg during the winter is the gasoline, winter blend, has less BTU's per gallon which means less mpg.

Also the EPA MPG standard for the 2010 Prius was conducted with regular gasoline with NO Ethanol. Here is another reason for a loss of 3 mpg or so. Seems odd that the EPA which leads me to believe loves the benefits of ethanol in our gas would do this.

So everything is against the Prius during the winter.

It is my expierence that even during the summer with ac on I get much
better mpg than winter with no ac.

al

 

This would be relevant if cars were still labeled with CAFE ratings. But EPA labels have long been discounted far more than the ethanol difference. And after EPA labels were sharply discounted yet gain in 2008, this E10 vs E0 is peanuts compared to the CAFE vs EPA difference.

 

Well it would seem that when the 2010 Prius model year epa mpg ratings were developed the fuel used was pure gasoline and not 10% Ethanol blend. So the epa for the 2010 Prius was average mpg of 50 MPG. So with 10% ethanol it would have been 47 mpg.

I would like the extra 3 mpg if I could but here in Oregon gasoline is mandated year long with 10% Ethanol Blend.

I think it would be feasible for the epa to require all passenger cars with gasoline engines to conduct their test with 10% ethanol blend because most states now require it.

al

 

Per the article I linked to in http://priuschat.com/forums/other-c...uth-about-epa-city-highway-mpg-estimates.html.

They do not measure actual fuel consumption.

 

My last tank was probably 45mpg (I forgot to note it!) but it's been a bit colder and we now have winter tires on.

Suprisingly though, we still haven't had an entire week of freezing mornings.

 

Pure gasoline was no longer required even when my 1997 car was tested. The EPA already had a published formula to translate oxygenated fuels back to a standard fuel. And as Cwerdna points out, the test doesn't measure fuel volume input, but rather emission outputs along with some of the fuel properties.

E10 reduces MPG only 3%, not 3 MPG as you portray. But the EPA label is already derated more than 30% from the CAFE rating due in large part to people's driving habits, much of that coming in the 2008 rescaling of the EPA figures. Compared to that entire 30% discount, the E10 loss portion of 3% is peanuts.

Your 2010 Prius has a CAFE rating of over 70 MPG on pure gasoline, which would translate to just over 68 MPG on E10. Instead of complaining about 47 on E10 instead of 50 on pure gas, you should be exploring why you are not getting 68 MPG on E10 itself.

As far as I'm concerned, that 3% E10 hit was already included in the EPA's major 2008 rescaling / downrating.

Right now all the different government ratings are derived from the same batch of tests, starting with the CAFE requirements. You are asking for a whole 'nuther round of government mandated tests with a different batch of fuel. I feel this is another layer of government regulation that we don't need. And it would only get worse as more states mandate E15.

 

I've seen what repeated short trips (dozen 1 to 2 mi, 3 to 6 minutes), spaced hours apart do to my FE in 50F weather, 37/35psi, dry, no heater .. drag FE from over 52 to 49.7....

wonder what short trips, freezing temps and high heat use would do? Drag it down to 44 on the gage?