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Fuel economy much lower than advertised

Discussion in 'Newbie Forum' started by Savalife, Nov 20, 2011.

  1. Savalife

    Savalife Junior Member

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    After driving 2980 miles, I find that my 2011 Prius III averages about 41 mpg (recently 38 mpg!) when I do manual calculations. Why so low? Here is some relevant information:
    1. ECO used for city driving, but not on the highway
    2. Tire pressure maintained at 35 psi front and 33 psi rear
    3. Average speed is usually about 28 mph (highway no more that 5 mph
    above speed limit)
    4. No fast starts or sudden stops
    5. Coasting wherever practical to reduce gas consumption
    6. AC kept at ~78 degrees during summer; heat kept at ~ 68 degrees in cold
    7. No heavy loads in car (I weigh 159 lb!)
    8. No roof rack
    I was expecting > 50 mpg according to published gas mileage for the model I purchased in July of this year.
     
  2. Paradox

    Paradox Prius Enthusiast / Moderator
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    How long are your average trips? Short trips also kill mileage. Some people find using ECO lowers their mileage rather then helping it. Driving style matters more than just choosing a mode, it's not an instant guaranteed mpg savings button. Try normal for a tank or two and see if it works better for you. People also run a little higher tire pressures than you have, so you can bump them up a bit, that will help. You also say no fast starts, but starting slow (slow enough to force the car to only use electric discharging the battery) can lower mileage since the engine will have to run more often to recharge the battery again.
     
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  3. frodoz737

    frodoz737 Top Wrench

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    Leave it in ECO at all times, increase tire pressures to 42 front 40 rear and try different driving patterns. My low tank was 36, best 61 with lifetime 50 mpg.
     
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  4. F8L

    F8L Protecting Habitat & AG Lands

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    Shorts trips are generally the culprit when some complains about low mpg. Imagine the mpg you would get in a conventional car.
     
  5. TonyPSchaefer

    TonyPSchaefer Your Friendly Moderator
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    2980?
    There are two important things in addition to what the guys have already said:you get better at driving the car and the car gets better at driving for you.

    What was you're previous vehicle? You don't have to radically change your driving habits but knowing the little tricks sure helps. Read the stickies in the Newbies forum and you will get a wealth of knowledge.

    Also, keep in mind that auto manufacturers are required by law to advertise what the EPA tells them in terms of mileage. So technically, a more appropriate name for this thread would be "Fuel Economy Much Lower Than EPA Estimates".
     
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  6. cwerdna

    cwerdna Senior Member

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    http://priuschat.com/forums/other-c...uth-about-epa-city-highway-mpg-estimates.html
    http://priuschat.com/forums/gen-iii...mileage-gets-worse-in-winter.html#post1411488
    Your Mileage Will Still Vary
    Many Factors Affect MPG

    Agreed w/Paradox's advice and comments. Without any more info, I'm guessing the OP has very short trips.

    Also, besides the car getting more broken in over time, the tires will be more broken in and more worn, resulting in real and apparent mileage increases: Tire Tech Information - Tire Rolling Resistance Part 3: Changes to Expect When Switching from Worn-Out to New Tires.
     
  7. txl146

    txl146 Member

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    I've been averaging 52.7mpg last 8500 miles without using any special techniques (no ECO, etc). 75% highway/25% city driving.
     
  8. qbee42

    qbee42 My other car is a boat

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    What is the temperature in the OP's area? I would suspect cold. That is also a mileage killer. I'm averaging only 41.4 on the current tank, down from 54 just a few weeks ago. In my case it is shorter trips and cold weather.

    Tom
     
  9. Pfcardwell

    Pfcardwell New Member

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    In St. Louis I am getting 50 plus. Bought Prius 2011 level 2 in October. Utube has a good Video on driving the Prius.
     
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  10. Pfcardwell

    Pfcardwell New Member

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    Here is the YouTube video.

     
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  11. Rokeby

    Rokeby Member

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    Savalife,

    :welcome: to PRIUSchat, hon. :cheer2:

    While I drive a Gen II and you have a Gen III, I think that I can
    contribute some general comments that should be helpful.

    As noted, short trips, less than ~5 miles for mixed urban driving are
    MPG killers.

    Those two or three mornings last week when it was mid 30s in the
    morning would have been MPG killers if you don't have your grills
    blocked.

    Heater use can be a big hit too. You need to use it -- full fan on high
    heat -- to defrost/demist -- but after that use it as little as you can
    until the engine is fully warmed up. For me last week, that was about 5
    miles.

    One trick is to turn the heater off when the car is not moving, like at
    stop lights. If you do this the engine will shut down at stops, even
    though the engine is not fully warmed up.

    Definitely pump those tires up to 42f/40r, good for 3-5 MPG.

    Remember that the EPA numbers are estimates from running the car in
    a non-real world test sequence. Your mileage will vary depending on
    many factors. Folks who buy their Prius in the warmer months often
    get accustomed to getting very good MPG without even trying. Well,
    those days are over until the spring. You'll have to use every trick you
    can find and read about here just to keep the MPG hit to 10% for the
    next 3-4 months.

    [Edit] FWIW, once it's been raining and there is standing water on the
    roadway, you can expect to see a 3-5 MPG hit depending on the depth.

    The Gen III folks have pointed out some threads that should be helpful.
    I recommend that you take the time to read them, even If they are
    quite long, there's lots of info and many subtleties to be mastered.

    Good Luck. :rockon:
     
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  12. wick1ert

    wick1ert Senior Member

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    Also see if you can park your car facing a different direction at night, if the sun comes up before you leave. I found that backing in my driveway results in my windshield being either just wet or clear rather than frosted over in the morning when I pull straight in. That's good for a couple MPG difference, esp given a shorter drive. It's much easier to get the back window cleared than the front, and it doesn't pull the engine heat into the car right away.
     
  13. jhinsc

    jhinsc Senior Member

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    Your mpg's are based on your driving conditions and your driving style. You can get low mileage just as easily in a Prius as any other car. You may not have any control of your driving conditions but you can modify your driving style and have a huge impact on your mileage.
     
  14. cycledrum

    cycledrum PSOCSOASP

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    Like others said, really short trips are likely the problem.
     
  15. J5A

    J5A Active Member

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    When I switched to normal mode from eco my mpg's increased by 6.
    It helps me feel less disappointed I'm not acheiving epa rating either, especially when I see so many are getting +50mpg's in colder climates than ours.
     
  16. bisco

    bisco cookie crumbler

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    maybe there's something wrong with your car.
     
  17. cwerdna

    cwerdna Senior Member

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  18. Danny Hamilton

    Danny Hamilton Active Member

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    I'm thinking this is the biggest culprit for this owner.

    Original poster has owned the vehicle for at least 19 weeks (first PriusChat post July 10), and claims 2980 miles.
    If we assume the vehicle is used as a daily driver and is driven on average twice a day 5 days a week, that works out to 190 trips in the vehicle.

    The average trip is 2980 / 190 = 15.7 miles.

    If the car has been owned longer than July 10, or is driven more than 10 times per week, then the average trip length is even shorter.
     
  19. bisco

    bisco cookie crumbler

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    probably shorter, cause i drive my gen II 7 miles each way for 14 miles a day and get betweem 55 and 65 mpg depending on weather. maybe he does a lot of 1 and 2 mile trips?
     
  20. bisco

    bisco cookie crumbler

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