Poor winter fuel economy

This question should really go in the fuel economy section. Answering the questions at http://priuschat.com/forums/gen-iii...-answer-these-questions-esp-if-youre-new.html would help.

However, yes, the Prius takes quite a hit on mileage in cold weather. Your short (at least the 4 mile drives) will yield "poor" mileage. Your tire pressure might've dropped significantly too, further hurting mileage. The engine always running might be due to your HVAC usage.

To prevent the ICE (internal combustion engine) from running to provide cabin heat while idling or at low speeds when the ICE is cold, do not use auto and set the fan to OFF unless the you must go above 42 mph (46 mph on the 3rd gen?) or your acceleration demands the ICE coming on anyway. To figure out when it's "ok" to turn on the fan w/heat above lo, you'll need to monitor coolant temperature with something like a ScanGaugeII - Trip Computers + Digital Gauges + Scan Tool. The 2nd and 3rd gen Prius, HyCam, NAH and Lexus HS 250h all share this behavior. I've confirmed it myself.

(Example: On 2nd gen Prius, while stopped, if you set the temp to "hi", fan to "lo" or above and fWT (Fahrenheit Water Temperature) is <=145, ICE will run. The moment you press fan off, ICE will stop. When you press any other fan speed, ICE will start.)

Usual further suggestions to improve winter mileage:
- engine block heater
- grille blocking

 

Yep, if it's a short trip, just wear a coat and gloves and leave the climate control off! I only turn it on if the windows star fogging up!

 

I also noticed that in another one of the OP's threads, he's changed the tires to "Michlein Ice X-12". I wouldn't be surprised if they have worse rolling resistance than the OEM tires, cause further drop.

Even if one changes from worn tires to identical new ones, there will be some hit. See Tire Tech Information - Tire Rolling Resistance Part 3: Changes to Expect When Switching from Worn-Out to New Tires.

 

With so short trip, in your case I'll make convertion to Plug-in, and not allow swith on the engine at all.

 

As above, it's the auto A/C system calling for heat that forces the engine to run. The engine will run if the coolant is below about 63C, and it takes a while to get it above that. The Prius engine is so efficient.

You will still be getting better mileage than you would in any other car sold in the US or Canada.

I will turn off the auto A/C at red lights to let the engine stop. Unless I'm too cold or the windows are fogging. Also, you'll find the front defrost works well at removing mist and frost from the inside of the windows even before the car is blowing heat. But with this on, the engine will be forced to run, as it also trips A/C auto. At least it does in the GII.

 

Depending on where you reside gasoline
is refined for climate. Winter blend gasoline
has less BTU's (energy content/"British Thermal Units") than
summer gasoline.

Also Ethanol gasoline with 10% Ethanol also
as a negative effect on MPG's.

All old Prius owners know that
summer is good for MPG
and winter is bad for MPG.

Here in northwest Oregon we average in the low 50's mpg during
the summer and 45 mpg in the winter

al

 

yes winter will lower you mpg.

You may have cuased some of the drop.
1. With different tires they will or can lower mpg.
2. You talk about running the battery down this will only lower you mpg cause the car has to burn more gas then convert it to electricity then charge the battery and then convert it back to ac from dc and then drive the electric motor. You loose alot of energy doing this so just burn gas when you need to ad don't try to use the electric motor to discharge to battery.
3. If the ICE is cold and you are asking for cabin heat the car will also burn more gas to warm up. You can avoid this by not turning on the heat untill a few miles down the road after the ice is warm.

 

Since when is low 40's for MPG bad?

Haven't you noticed the other automakers bragging about achieving 40 MPG under optimal (highway speeds only during the summer) conditions?

Looks to me that the worst for Prius is the best for most others.
.

 

Winter will take a toll on all vehicles. Winter gas, longer warm ups, heater operation, defrosting, shorter daylight hours, longerheadlight operation, greater friction pushing through rain or snow, slower traffic more prone to stop and go, and etc. Waiting to pick up the kid's at school with the engine keeping the cabin warm will also take a terrific toll. What I am waiting to read are complaints that the EV's mileage has dropped for all the same reasons (except winter gas). Wait until we reads complaints that the Volt's engine runs when not needed solely to keep the pollution components hot and operational.

I am satisfied that for any car to achieve an average of 50 mpg, (a barrier almost like the sound barrier) all the variables must be close to ideal (gasoline, tire pressure, temperature, dry pavement, traffic and etc.)

 

liteguy ..... I now have 32K on my 2010. I have enjoy sufficient miles to really appreciate the genius of the Prius, but less than ideal conditions will reduce the fuel efficiency. Find comfort in the fact that other vehicles will be impacted as well.

In the Fall I drove across the country (7500 miles). I monitor every mile, every gallon of gas. I was achieving 52 mpg for 1000 miles, then we had a day of terrible rain. Fuel efficiency dropped to 44 mpg. Then the following day, it was up again. Tire pressure, head wind, load, all take a toll. Winter will cut mileage if your driving is short trips, turn off the car, then start up for another short trip, then stop .... The ICE will run much more often than in the Summer .... I presume to keep the anti-pollution components hot??

I agree ... when it is cold, I am going to run the heater .... I am willing to sacrifice a few mpg.

BTW .... I just purchased a 2011 Honda AWD. I really like the vehicle, and already it has proven of value (two days of deep snow). But it has made me realize how great the Prius really is: the smart key ignition; door unlocks when approach with key; garage opener on mirror; self dimming mirror; I really appreciate the engine does not run when sitting at a light; or the A/C (when it was hot) will cool while parked waiting for the wife; and the hybrid system readout provides so much useful, and clearly legible information (it's OK that it is not 100% accurate .... it is consistent).

My ONLY regret is that I have 32K on my 2010, but I have driven it across the country twice this year. Both great, comfortable, relaxed trips.

Good luck with your.

 

The Puget Sound region is suffering extreme blizzard conditions *** right now, creating extreme congestion on the highways and havoc on the other roads. Today's commute produced the worst mpg of the year. Yet my Prius still consumed less fuel than my Subaru would burn merely warming up and idling in its parking space, without moving an inch, for the same amount of time (greatly extended by the congestion).

***Translation for inland folks accustomed to 'winter': A light dusting of snow, 2" at my house.
- - - - - - - - - - - - - -
PS. It is past 11:30 pm, and there are still 4 major blockages on interstates, more on the lesser roads. TV crews are interviewing drivers who have been stuck in traffic jams 4 to 6 hours. Many will not get home tonight, some will run out of fuel.

This is why I took the Prius this morning, not the Subaru. Prius easily handles the every-third-year commute that turns into a half-day adventure in interstate parking. Congestion renders Subaru's abilities meaningless down at this elevation, until the rare cases where the snow depth exceeds the ground clearance of most cars.

Fortunately, I was able to stay at work until the traffic reports and maps revealed a route home that would take less than double the normal time.

 

sorry slightly off topic, kind of a left turn, just out of curiosity, when you talk about blocking the grill, how much do you block (winter versus summer), how do you monitor the engine temp (scangauge?)and what do you use to block the grill. tks as this will be my first winter with this car.