2017 Prius Two sudden drop in MPG

welcome!
how many tankfuls have you calculated at the pump at the lower mileage?

 

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.

 

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?

 

No. Still researching.

 

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

 

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.


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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.

 

I still can’t see how it’s dropped so much. Mine started in November. Maybe it got Covid and hasn’t recovered.

 

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.

 

No, it’s the same commute I’ve been doing for 15 years.


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