Cold Weather Mileage

I'd say since the weather really turned noticeably colder, my consistent 50-51mpg in overall driving and occasional trips of 55-60 have now dropped to a consistent 48mpg and the best I've done in the past two weeks is 51.5. So yeah, about 2mpg, maybe a a bit more. I'm right at 5,000 and had Toyota put synthetic in both for the colder weather and for me, more importantly, to make me feel a little better about when I get to 6,000 or 7,000 for my next oil change because of scheduling issues.

 

Northeast, Southwest, and everywhere in between .... MPG drops with cooler temperatures.

 

Do a search on this site for 'grill blocking" A simple piece of pipe insulation stuffed in the grill openings brought our "coo" weather (45-50f) up about 2 mpg. Warms up faster, better heat. Read the post and decide how much to block your own for your climate.

Icarus

 

Just to add my experiences of late to the first post:

I live in Pennsylvania and we received our first snow this weekend. My wife told me something was wrong with our Prius' MPG and wanted me to take a look. I was pretty surprised at what I found. After ten minutes of driving in the cold weather, I was only averaging about 21 MPG. After 15 minutes, however, it went back to about 51 (still not as good as before...but pretty great relatively speaking).

I was going to ask if the cold weather was the culprit...but it seems obvious that it is. I'll take a look at the grill blocking posts.

Thanks.

 

<div class='quotetop'>QUOTE(hybridbrian @ Nov 20 2007, 08:54 PM) [snapback]542228[/snapback]</div>

I've had my Prius since the end of May, and have consistenly been getting pretty good miles per gallon. Having experienced a noticeable drop in mpg on my current tank of gas, I found this forum to try to find out why. As others have noted, cold weather is a culprit (I'm in NJ). Is it true that generating heat requires that the gas engine run (as in a conventional car)? Now that daylight savings time has ended, the evening commute is done in the dark. Does the use of headlights hurt mpg? Do the headlights draw enough power
to require more gas engine operation at night than in daytime? Thanks.

 

<div class='quotetop'>QUOTE(egertz @ Nov 20 2007, 06:59 PM) [snapback]542255[/snapback]</div>

Headlight draw is small enough to be insignificant. Consider blocking your grill.

Icarus

PS I drive with headlights on all the time. Old Motorcyle habit. We get 52-53mpg on most tanks

 

<div class='quotetop'>QUOTE(icarus @ Nov 19 2007, 06:34 PM) [snapback]541699[/snapback]</div>

There have been a couple of very good threads about grill blocking. The "original" thread that discusses this topic was one started nearly a year ago by Tony Schaefer entitled First Morning with a Blocked Grill. There are discussions within the thread regarding the reasons for blocking a grill, the benefits of doing so, warnings about temperature extremes and directions for doing the "grill blocking" yourself. Along with these directions you'll find pictures of the end result for a few different ways of accomplishing the task. There is even a graph showing one poster's claim that the grill blocking has resulted in a 4% increase in MPG even with a very short commute.

Here are some example photographs (and a video) from the thread:

1. The basic pipe insulation used by Fire Engineer (Wayne) and Tony Schaefer.
2. A view of the compression-fit insulation pulled back from the grill -- to show how to install (insert) the insulation in the grill.
3. A photo of the Doc's (Efusco's) version of grill blocking. This one uses a different type of pipe insulation, and also has a more complete cover of the grill. Efusco's version uses the full diameter of the pipe insulation. The whole piece covers the grill and is held in place with zip ties.
4. Another installation like Efusco's, only this time the pipe insulation is held in place with the adhesive that comes on the material. This is a clean look with no zip ties. The poster (usbseawolf2000) also includes a link to a video of his installation.
5. Hobbit's version (or at least a link to it) in which the blocking is behind the front grill.
6. Another modification of the style shown earlier by Efusco. This one uses zip ties on the top grill just like Efusco, but the bottom grill's zip ties are set up so that the pipe insulation can be adjusted to allow more or less air flow. The look on the bottom grill is more like a quilted blanket (IMHO).
7. The Combo Method: This one uses a compression fit on the upper grill and the full-cover, zip-tied method for the lower grill. This poster started with the pipe insulation used by Tony Schaefer but switched to the pipe insulation used for covering air conditioning pipes. This other insulation is a different type of foam that is more flexible at lower temperatures. It also is a bit darker in color and has a smoother finish. It also was used by Efusco.
8. The "Cut-to-Fit" look -- In this one the poster ("JimN") cut the pipe insulation into 8 separate pieces for the upper grill. This gives a very clean look.
9. The latest look. Whereas JimN got a very clean look by cutting pieces to fit, I just cut the pipe insulation to fit (tightly) lengthwise. By using the foam for air conditioners (darker and without the open cells showing) and cutting it down to narrow pieces fit to the whole length of the grill, I think the effect is to make the foam nearly disappear. This is my attempt to get it done after reading through the past year's worth of postings.

I hope this helps you navigate a very long thread with LOTS of valuable information.

I don't want to discount other, valuable threads. I just happened to have relied on the one noted above. Here are other threads to read:

1. Blocking the grill
2. My attempt at grill blocking This thread shows a VERY CLEAN installation of the pipe insulation. The poster refers to it as an "OEM" look -- and I see why. This is what I was looking to get, but I don't think I had the time and patience to accomplish this great look.
3. Quick grill blocking question
4. Sorry if this is stupid . . . but what is grill block? This is a newer, shorter thread that re-directs the reader, but offers some comments as well.

a priori

 

<div class='quotetop'>QUOTE(efusco @ Nov 20 2007, 10:26 PM) [snapback]542299[/snapback]</div>

I agree. I'm sure many new posters will find your post very helpful!

 

<div class='quotetop'>QUOTE(efusco @ Nov 21 2007, 01:26 AM) [snapback]542299[/snapback]</div>

Thanks . . . but you did the work!

<div class='quotetop'>QUOTE(F8L @ Nov 21 2007, 02:25 AM) [snapback]542328[/snapback]</div>

Thank you. I hope people do find it helpful.

Still, I'd like to get some help making the links work correctly.

Anyone . . . Bueller . . .?

 

Just to mention another thing that happens in the winter - in some places - here in Oregon the gas stations switch to "winter gasoline" around Oct/Nov. I've read in some local sources that gas mileage can drop by 10-20%, as the winter gasoline is less volatile but also has less energy. I noticed last winter and again this winter, that all of a sudden our Prius' mpg dropped by around 5 MPG. We get about 45 MPG in summer - I know that's not so great, but our daily route is not good at all for mileage, I've become resigned to it. So all of a sudden our mileage drops to around 40 MPG from the winter gasoline. Then we switch from the OEM Integrities to Blizzak snow tires, and the temperature drops into the mid-low-forties (nights in the mid-low-thirties), and our mileage drops even further. This winter, I will try blocking the grille and using a block heater.

 

<div class='quotetop'>QUOTE(efusco @ Nov 21 2007, 06:58 PM) [snapback]542679[/snapback]</div>

Going back to it, I find that the links only take me to the top of the page containing the particular post I've referenced. Are you being directed to the correct post?

 

<div class='quotetop'>QUOTE(efusco @ Nov 23 2007, 11:45 AM) [snapback]543226[/snapback]</div>

That's the funny thing about all of this -- that's the way I did it! I think I may need to try this all over again, because I just don't understand why (how?) it didn't work.

 

Is there a drop in mileage once the car is warmed up? I'm grill blocking, keep heat off or on low.

I filled up and reset yesterday after the car was warm and got a 75 mpg/20 mile segment on the way home in high 30s temps, which is right up with my best summer runs from cold start.

Has anyone found a good warm up method (rpm/speed)? I've altered route slightly to a 45 mph road and try to hold 1600-1700 rpm for the second 5 minutes which gets me to a sub 40 p&g friendly stretch and I want to be warmed up by the time I get there but was just under s4 temp when I got there yesterday.

 

I was averaging 50 - 52 mpg in the warm months here in Illinois, but now that winter has started, about the best I can muster up is 45 max. What are the secrets to getting better mileage out of the Prius during winter months??

 

My recommendations:

1. keep speeds below 25 mph for first, two miles - this minimizes fuel burn while the ICE is warming up and relatively inefficient. Cutting through the neighborhood works great using "N" to coast as much as possible with modest acceleration.
2. stay in 15-38 mph and 45-65 mph range for up to two miles from destination - these are fuel efficient regions and avoids transiting 42 mph, a boundary between control laws.
3. keep speeds around 25-30 mph for last, two miles - this maximizes the EV mode at the end and tops off the mileage.

Other recommended practices include:

• block heater - this can cut the warm-up period in half, from two miles to one mile.
• grill block - a form of radiator block, this reduces heat loss at low power settings and improves warm-up.

To get an idea of what these changes can do, try the following test:

1. measure MPG for first two miles: zero MFD and a trip meter and measure and record the MPG and distance.
2. measure MPG for rest of trip: re-zero MFD and trip meter and measure and record the MPG and distance.

This will give you insight to what cold weather driving is all about. As you adopt some of these techniques, you'll get feedback on what works and what doesn't work.

GOOD LUCK!
Bob Wilson