2017 Prius Two sudden drop in MPG

Discussion in 'Gen 4 Prius Fuel Economy' started by Scara36, Jun 17, 2020.

  1. Scara36

    Scara36 New Member

    Joined:
    Jun 16, 2020
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    Location:
    Arizona
    Vehicle:
    2017 Prius
    Model:
    Two
    I bought my 2017 Prius Two in October 2018 and have had wonderful mpg until March of this year. I began commuting to a new job in February 2020 and my mpg actually increased because of the new driving situation. I was getting about 53-54mpg with a combination hwy and city driving (based on my Trip odometer and fillups). One Friday after work, I got gas, drove home, parked the car with 54 mpg showing. The next morning, I began a drive that would be about the same distance, but after about 5 miles, my mpg began to drop. At first, I wasn't too concerned because as long as it stayed above 49, I felt it was acceptable. By the time I got to my location, it had dropped to 38mpg! And, it's been horrible ever since. I struggle to get 44-45mpg, understanding that summer in southern AZ means using more AC, but the history and my experience showed that I still should be getting no lower than 48.7 mpg (approx). Manually calculating my mpg when I fillup, it's typically off by about 2mpg, but I know that. I've got Toyo tires inflated properly, and until COVID hit, I hadn't changed my driving habits. The dealership I've taken it to twice now basically said to switch my view to see the overall mpg and that there was nothing wrong. (Big Two Toyota in Gilbert, AZ) Please tell me someone else has had a similar experience.
     
    Marcius likes this.
  2. bisco

    bisco cookie crumbler

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    2012 Prius Plug-in
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    Plug-in Base
    welcome!
    how many tankfuls have you calculated at the pump at the lower mileage?
     
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  3. Scara36

    Scara36 New Member

    Joined:
    Jun 16, 2020
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    Location:
    Arizona
    Vehicle:
    2017 Prius
    Model:
    Two
    Without checking my log, I’d guess 6-8 tankfuls
     
  4. Marcius

    Marcius Junior Member

    Joined:
    Jun 28, 2020
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    Location:
    So Cal
    Vehicle:
    2017 Prius
    Model:
    Three Touring
    I have a 2017 3 Touring. I have the same before and after mpg that you have above for almost the same period. I'm in CA. It's been hot, plus I went on a long road trip probably logging about 1k miles through the CA smoke. We came back from the trip, and it seems that's when mpg took a hit. I thought maybe the ashes clogged up the new air filter I just put in. But, it looked okay. I sprayed air through it just in case it was clogged, but didn't notice any real dirt or ash buildup. So, I'm still on the hunt for where those lost mpg's went.
     
  5. Jbania

    Jbania New Member

    Joined:
    Oct 18, 2020
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    Location:
    New York City
    Vehicle:
    2017 Prius
    Model:
    II
    I'm encountering the same thing with my 2017 Prius II. Additionally, the stated miles per gallon on the dashboard on my last 90 miles trip read 61.5 mpg, while the actual mpg was closer to 44 mpg. No idea what's up with the discrepancy. Have you figured out what might be going on with your car?
     
  6. Marcius

    Marcius Junior Member

    Joined:
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    Location:
    So Cal
    Vehicle:
    2017 Prius
    Model:
    Three Touring
    No. Still researching.
     
  7. Derek kelleher

    Derek kelleher New Member

    Joined:
    Dec 30, 2020
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    Location:
    California
    Vehicle:
    2017 Prius
    Model:
    Two Eco
    Yeah have come across the same myself. Did 50k miles and was getting 55 MPG from my Eco II . Over the last 5k miles it has dropped to 46-47. even replaced the air filter thinking that it could have been clogged.

    Regards
    Derek
     
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  8. JasonB121

    JasonB121 Junior Member

    Joined:
    Mar 28, 2020
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    Location:
    AZ
    Vehicle:
    2017 Prius
    Model:
    Two
    I have 2017 Prius two I bought and have serviced at Big Two Toyota as well.
    I was rolling along with 60k and getting 48mpg on the worst days with hills and heavy throttle. Then on good days I’ve seen 60mpg on my commute for a week.
    Then I bought new tires and the mpg went downhill to 36 to maybe 48 on my best of days. The tires are Continental fuel savers and they aren’t saving me anything.
    I’m going to see how it goes and if it’s going to be in the low 40s when I’m doing everything to conserve fuel, I’ll get a different car and get mid 30’s but more fun to drive.


    iPhone ?
     
  9. Frankiie

    Frankiie Junior Member

    Joined:
    Feb 18, 2021
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    Location:
    Chino
    Vehicle:
    2017 Prius
    Model:
    Two
    I got the very similar case, and still puzzling about the drop of the MPG.
    Mine is 2017 Prius 2, been consistently getting 54mps till Dec 2020 around 52K mile at south California. After replacing four new tires, and been consistent on the MPG, the MPG suddenly dropped to 48-50MPG one day in December, and since then. Have visited two dealership for service, got the fuel system and air system cleaned, but the MPG is still below 50, and engine running is little rough and harder than before when accelerating. Asked the dealership whether should have the transmission fluid changed. The dealer recommended it as not necessary and expensive.
    By now still puzzling whether it would come back to 54MPG when winter is over.
     
  10. JasonB121

    JasonB121 Junior Member

    Joined:
    Mar 28, 2020
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    Location:
    AZ
    Vehicle:
    2017 Prius
    Model:
    Two
    I still can’t see how it’s dropped so much. Mine started in November. Maybe it got Covid and hasn’t recovered.
     
    MIkeDr likes this.
  11. jerrymildred

    jerrymildred Senior Member

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    Location:
    Tampa, FL
    Vehicle:
    2017 Prius Prime
    Model:
    Prime Premium
    Welcome to PC, Frankiie. The dealer is half right. Changing the transaxle fluid won't help the mileage. But it's not expensive and lots of people consider it to be good preventative maintenance. You can buy the Toyota ATF-WS for about $50 and it's easier than changing your motor oil. Just be sure the car is level so you get the right amount put back in. But, again, any effect on mileage will be too small to detect.

    Maybe it doesn't have COVID, but is it making shorter trips than it used to? That'll make a big difference. Especially if your part of AZ is cold this time of year.
     
  12. JasonB121

    JasonB121 Junior Member

    Joined:
    Mar 28, 2020
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    Location:
    AZ
    Vehicle:
    2017 Prius
    Model:
    Two
    No, it’s the same commute I’ve been doing for 15 years.


    iPhone ?
     
    jerrymildred likes this.
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