Cold Weather Consumption

First, Read the posts on grill blocking and it will answer most of your questions better.

In short, the engine needs need to run efficiently. It will run all the time until the coolant reaches ~120f. It really wants to run ~185. Since the heater is only getting "waste heat" from the engine, running it with a cold engine will only draw down your mileage. (It is amazing how man people don't understand how car heaters work!)

I can drive 20 miles before my car is fully warm, and that is with the grilled blocked, and the temp ~40f. An engine block heater will help, because you will start with warm coolant.

Icarus

PS A gasoline engine will run most efficiently when it gets to it's design temp, in the case of the Prius ~190f. Running colder than that requires the ECU (computer) to run an extra rich air/fuel mixture to run properly,, wasting gas. Just as in the old cars, the choke served to richen the mixture to get it to run cold. Same with fuel injection.

PPS. Another couple of reasons to run engines at design temps. The internal parts are designed for their EXPANDED sizes. Piston rings seal better, less wasted fuel in blow by. Bearing clearances are better, allowing less oil to be scraped off by the rings etc.

By running the engine warm also helps the oil, allowing water vapor to boil off rather than forming acids in the oil. (water vapor created by the said blow by) Finally, and I guess I'll stop, running the engine hot keeps the exhaust system warm, allowing the catalytic converter to work better, (fewer emissions) AND by keeping the pipes hot allows moisture to boil out of the pipes and muffler(s) therefore decreasing the potential for rust.

 

Hey, glad I'm not alone!

I rarely run the heat, for reasons Icarus cited. It's personal preference and a tradeoff: the highest MPG possible vs. a cozy cabin. I can compensate for the latter by bundling up.

 

I thought this was a thread about winter TB.

Tom

 

My TB seems to be in remission, just the nagging cough!!

Seriously, look into the threads about an engine block heater and grill blocking. A scan gauge is a great too to really see how the temps work. The coolant thermos will keep the coolant warm even for a couple of days. @ days without driving the car, with temps in the 30's, started the car and it was ~70f. Even with that head start, six miles of steady 50mph on level road and the temp was only ~140. Another six miles on the freeway, (and turning the heat on) and the temp got to 174.

The Prius coolant thermostat STARTS to open ~185 and isn't fully open until ~205 if memory serves. The problem many people have with short(er) commutes is the car NEVER gets warm, perhaps all winter, with the mileage suffering as a result. An engine block heater is a pain to plug and un-plug but would pay dividends in that case. (I don't use one 'cause of the hassle factor, plus we drive ~25 miles whenever we leave home so it gets warm)

Grill blocking on the other hand is easy to do, cheap, and you can leave it in almost year round depending on your location.

Keep reading up, and good luck,

Icarus