1. Attachments are working again! Check out this thread for more details and to report any other bugs.

MPG drop with colder temps?

Discussion in 'Gen 3 Prius Main Forum' started by wheelsup, Nov 2, 2011.

  1. wheelsup

    wheelsup Junior Member

    Joined:
    Sep 3, 2011
    86
    14
    0
    Location:
    Raleigh, NC
    Vehicle:
    2010 Prius
    Model:
    II
    Was getting around 52.5 MPG in warmer weather, changed the tranny fluid and normally people report an increase in MPG. We're now getting around 50.5 MPG, so a 2 MPG loss. In addition, temps have gone from around mid-80s to mid-60s. Wondering if that would explain the MPG drop?
     
    #1 wheelsup, Nov 2, 2011
  2. cwerdna

    cwerdna Senior Member

    Joined:
    Sep 4, 2005
    12,544
    2,123
    1
    Location:
    SF Bay Area, CA
    Vehicle:
    2006 Prius
    #2 cwerdna, Nov 2, 2011
  3. DavidA

    DavidA Prius owner since July 2009

    Joined:
    Jul 14, 2009
    2,328
    1,812
    18
    Location:
    Chicago western burbs
    Vehicle:
    2017 Prius Prime
    Model:
    Prime Advanced
    Sure. Absolutely normal. I'm in Chicago, and move from the high 40's/low 50's in the summer down to the high 20's and low 30 mpg's in the winter.

    The ICE will run longer to warm up the coolant, and the traction batteries aren't as efficient when cold. Even if the battery power is at max, the computer will run the ICE right away due to the temps being in the 60's or less.
     
    #3 DavidA, Nov 2, 2011
  4. fuzzy1

    fuzzy1 Senior Member

    Joined:
    Feb 26, 2009
    17,286
    10,140
    90
    Location:
    Western Washington
    Vehicle:
    Other Hybrid
    Model:
    N/A
    Down only 2 mpg so far? That is great, I'm down almost 5 mpg already. This fall's figures are not posted yet, but look at this graph for my past winter mpgs. Drivers who like cabin heat and don't install grill blocking will see even worse winter drops.

    And be sure to read Cwerdna's links, which point to plenty of detail on this annual topic.
     
    #4 fuzzy1, Nov 2, 2011
  5. spiderman

    spiderman wretched

    Joined:
    Jul 5, 2009
    7,543
    1,558
    0
    Location:
    Alaska
    Vehicle:
    2010 Prius
    Model:
    II
    Slap some studded snow-tires on it and then you are talking a hit. I am about at my 10mpg winter hit at the moment.
     
    #5 spiderman, Nov 2, 2011
  6. F8L

    F8L Protecting Habitat & AG Lands

    Joined:
    Aug 14, 2006
    19,011
    4,081
    50
    Location:
    Grass Valley, CA.
    Vehicle:
    Other Non-Hybrid
    Model:
    N/A
    You tried, Andrew. Lmao
     
    #6 F8L, Nov 2, 2011
  7. tonyrenier

    tonyrenier I grew up, but it's still red!

    Joined:
    Jun 29, 2009
    362
    44
    13
    Location:
    Green Bay, WI
    Vehicle:
    2010 Prius
    Model:
    III
    60-80F seems to be ideal for the Prius, probably true of other cars too. I have now problem getting mid 60s mpg in the summer (that's calculated for a tank) I’ve had one tank, last year at nearly 70 mpg calculated. No hypermiling or pulse and glide, just drive sensibly and anticipate lights, do the speed limit, keep the junk out of the car.
    Winter is a whole different can of worms. I should get an engine block heater but I do block my lower grill. I usually get upper 40s again calculated. In winter I usually get better hiway than city mileage. Use the heater at an absolute minimum, or your mpgs will really go down with the car not always shutting down at stops.
    What part of the country do you live in?

    I have 55.2 calculated total mpg for the life of the car-30K+.
     
    #7 tonyrenier, Nov 2, 2011
    1 person likes this.
  8. firepa63

    firepa63 Former Prius Owner

    Joined:
    Jul 23, 2005
    1,761
    208
    0
    Vehicle:
    Other Hybrid
    Model:
    N/A
    Check your tire pressure...
     
    #8 firepa63, Nov 2, 2011
  9. wjtracy

    wjtracy Senior Member

    Joined:
    Sep 19, 2006
    11,321
    3,590
    1
    Location:
    Northern VA (NoVA)
    Vehicle:
    Other Hybrid
    Model:
    N/A
    I thought Alaskans were supposed to go to Hawaii for the winter.
    There your MPG would be better.
     
    #9 wjtracy, Nov 2, 2011
    1 person likes this.
  10. tumbleweed

    tumbleweed Senior Member

    Joined:
    Oct 3, 2005
    4,067
    687
    0
    Location:
    Eastern Oregon
    Vehicle:
    2010 Prius
    Model:
    V
    I am seeing the typical 5 or 6 mph hit here, winter gas, car running more to keep itself warm, and more wind resistance from cold air. I add air to keep tire pressures about the same.
     
    #10 tumbleweed, Nov 2, 2011
  11. spiderman

    spiderman wretched

    Joined:
    Jul 5, 2009
    7,543
    1,558
    0
    Location:
    Alaska
    Vehicle:
    2010 Prius
    Model:
    II
    I will have to tell my wife that, thanks. ;)
     
    #11 spiderman, Nov 2, 2011
  12. wheelsup

    wheelsup Junior Member

    Joined:
    Sep 3, 2011
    86
    14
    0
    Location:
    Raleigh, NC
    Vehicle:
    2010 Prius
    Model:
    II
    I'm not sure how someone would get a consistent mid-60's on this car without drafting. Highway speeds are under 50 MPG and city is maybe just above that. Even a constant 35-45 mph you won't get anywhere near 65 MPG, and that doesn't account for lights. I did see 59 MPG on my test drive but that was all downhill. Going the other way the mileage dropped to average around 50.

    Thanks for the info everyone I was hoping I hadn't screwed something up with the tranny fluid change. I suppose all cars lose mileage in the winter but it's just much more noticeable with this car. A 0.5 MPG drop in a car that gets 25 MPG is much less noticeable than a 1-2 MPG drop in our cars.
     
    #12 wheelsup, Nov 2, 2011
  13. skibum

    skibum Junior Member

    Joined:
    Sep 15, 2010
    33
    10
    0
    Location:
    New England
    Vehicle:
    2010 Prius
    Model:
    II
    I get in the high 50's for MPG, it isn't that hard to do, first pretend you don't have brakes, keep the tires at max, don't accelerate hard and lastly if you need to go up hills don't get the car into the "red" zone. FWIW I do between 60 and 70 on the highway.

    I could get over 60 mpg by never going above 55 on the highway or by drafting behind a big truck :) but it isn't worth my time.

    You should check your tire pressure before every fill up.

    Gerry
     
    #13 skibum, Nov 4, 2011
  14. walter Lee

    walter Lee Hypermiling Padawan

    Joined:
    Oct 26, 2009
    1,126
    376
    5
    Location:
    Maryland
    Vehicle:
    2010 Prius
    Model:
    III
    My fuel efficiency has dropped about 3mpg in October. Im hypermiling so that translates to a drop from 70mpg(Sep) to 67 mpg(Oct) per tank. I wouldn't attribute the October fuel efficiency loss to to temperature, if it wasn't for the fact the temperature has drop further about Oct 20th and I am noticing an additional 4 mpg loss in energy efficiency which translates to about 63 mpg. Some folks say that it not just do to the cold temperature but to Reformulated Gasoline - not sure. I've notice that If I warm up and drive the car for short 5 minute trip errand that if I drive the car about 30 minutes later (when the engine is still warm) and then drive it for longer 60 minute trips (my scangauge reports the Prius MPG to be in the 80 mpg range). Just starting the Prius with a ICE that is already warmed up can make a big difference wrt to the MPG. I've notice that when its raining or snowing my mileages usually drops too. When it rains my MPGs tend to go south, so when it rains more often - my overall MPGs suffer too.
     
    #14 walter Lee, Nov 5, 2011
  15. wheelsup

    wheelsup Junior Member

    Joined:
    Sep 3, 2011
    86
    14
    0
    Location:
    Raleigh, NC
    Vehicle:
    2010 Prius
    Model:
    II
    What are you guys using for tire pressure. IIRC the manual states 34/32, which seems really low. On my Volvo the fronts can go to 38 and rears 42 IIRC.

    To get an accurate MPG you need to do the route in reverse. Just saying you got XX MPG doesn't mean anything if you don't go back from where you came. Reason being you could be going downhill the whole way, inflating your MPG.
     
    #15 wheelsup, Nov 5, 2011
  16. fuzzy1

    fuzzy1 Senior Member

    Joined:
    Feb 26, 2009
    17,286
    10,140
    90
    Location:
    Western Washington
    Vehicle:
    Other Hybrid
    Model:
    N/A
    YouDon'tRC. Page 557 of the Owner's Manual lists 35/33 for 15 inch wheels, 33/32 for 17s.

    But mine were delivered at 40, and I prefer to keep them near sidewall max. The selling / servicing dealer has no quibbles with that. But the one other shop to touch the car did have a problem with that, and reduced the pressure. Unfortunately, they didn't account for temperature and elevation effects, resulting in underinflated fronts.

    This is the highest placard pressure of any car I've owned. The old Hondas were listed as 26 psi, which I abandoned after discovering they hydroplaned too easily.
     
    #16 fuzzy1, Nov 5, 2011
  17. jamieq

    jamieq New Member

    Joined:
    May 21, 2008
    2
    0
    0
    Location:
    Anchorage, Alaska
    Vehicle:
    2008 Prius
    Model:
    II
    We do :) but, sadly, there are no Prius renters in Hawaii :eek:
     
    #17 jamieq, Nov 7, 2011
(You must log in or sign up to post here.)