cold weather preparation

A Hybrid Owner’s winter survival guide - CleanMPG Forums covers most of the things you'd want to do.

Short answer is most people use foam pipe insulation instead of cardboard.

 

Besides the front grill, you can also put some short pieces of foam pipe insulation here:



Block heater is a good idea too. We use ours year 'round, and it's much milder weather for us.

To answer your winter mileage drop question, I'd say multiple reasons:

* Gas companies reformulate their gas in winter, and the reformulation tends to drop mileage a bit.

* Rain/snow increase rolling resistance.

* More driving in the cold/dark conditions: headlights and blower/heater impact mileage.

* An engine runs most efficiently when warmed, and warm up takes longer in winter.

* Parking outside sub-zero ices up your windshield, and thawing it out by idling eats gas.

* Winter driving just tends to be more short, necessity trips, tough on mileage.

 

Add to those reasons above, if the A/C system is demanding heat the engine will usually be required to run to produce it. So no shut-down at lights etc.

 

I have a block heater for a Prius brand new in the box. It never got cold enough in the last few years here in Florida to warrant using it. I would like to sell it. If interested please pm me. I take Paypal btw.

 

These are good information! If I may ask one question ( i do not mean to hijack this thread from the OP), how cold does it have to be to warrant these measures? I live in SoCal where it may get to 50-ish F on a regular winter day (lower temps occasionally, but not by much).

Thank you!

*edit* I did some more reading and found a good chart in the cleanmpg forums regarding blocking and temperatures. However, if anyone has practical information regarding Southern California winters / effects on the Prius, it would be much appreciated!

 

The nice thing about using pipe insulation is it keeps -other- things out of the engine compartment. Things like salt spray and road sand. Ethafoam is what it's made of though there is also a more flexible type that feels like foam rubber). It's used in refrigeration.

Put it on from the front, not from the inside. I take several longish zip ties and insert them through the grill, leaving them unconnected. Then I put the pipe insulation over the grill and connect the zip ties over it. Quick and easy.

As far as -when- you can use it, it's too much when the outside temp. is over about 70-75F. You can just block the -lower- grill in those temps. But at any rate, if you want to use grill blocking in marginal conditions, you really need a Scangauge or similar to watch the coolant temps. Or listen to the fan. If it's running a lot it's time to remove foam. Nice thing about the above way of installing it is it's easy to remove. If you use -removable- zip ties you can remove the foam and put it back without cutting the ties.

Here in Edmonton we don't get hot -ever-. Hot being southern California or Texas temps. I had both grills covered a few years ago when we had an early fall heat spell near the end of September (got up to 75-80F!!). The fans ran but coolant never got to 95C. It boils at about 120F. I DO have a Scanguage.

 

I do the pipe insulation method and it is such a tight fit that I do not need to fasten them with zip ties or anything.

I simply cut little slits in the foam to accept the supports in the grille and allow the foam to push into the grille a bit tighter. This keeps the foam in the grille nice and tight all winter such that I almost have to peel them out come spring.

Here is a pic of the foam installed on my car.

 

I don't see much drop off until it gets below actual freezing temperatures. When it's normally in the 20's (F) or colder then the engine takes noticeably longer to warm up. As you may know, the ICE doesn't actually turn off until the coolant temperature is 157'F (generally more if the heater is turned on also, which some people like to do in those temperatures, I only turn the heat on if the windshield needs defrosting or it's a longer trip). That's where the engine block heater really helps (it's not just to make startup easier).

Short trips magnify this effect, since more of your trip (perhaps all) is spent on the cold engine, and therefore no engine turnoff. This is best checked with a Scangauge or similar, the MFD can be a bit misleading, but you'll still see the results in the mpg.

Hint: use the auto setting on the heater - if you put the fan on high right away you may have a psychological factor of hearing the air move, but it's still only moving around cold air until the engine warms up enough to provide heat to the cabin. The auto setting will ramp up the fan as heat becomes available.

 

Actually I can see a slight difference in the coolant temperature and time to get to stage 3 (monitored on a scangauge), now that it's in the 50's and I park outside (normally I park in the garage). But it's still a minor change, it's going to take more than that for a noticeable drop in mpg.