Why the sudden drop in our 2012 Prius gas mileage?

Asked by May 25, 2014 at 04:56 AM about the 2012 Toyota Prius Three

Question type: Maintenance & Repair

The MPG on our Prius recently dropped from 52 to 44.  The drop occurred shortly after we took the car to a dealer for the software related recall fix.

17 Answers


There is your answer. But some owners who had the recall done reported no change to some saying their MPG dropped. I guess it's how you drive if your going to notice such a thing. Open this link, it will take you to some Prius owners who did the update.....http://priuschat.com/threads/who-has-done-their-recall.137632/

15 of 15 people found this helpful.

I had my 2012 Prius in for the recall and after the reprogramming there was no change. Where we have seen change is if the weather is cold (below freezing) and if it is raining (water on road seems to effect mileage) .. If driving habits are the same - and these two did not occur - I would take it back to dealer.


I had our 2010 Prius Two for software recall in June and noticed a drop in MPG from about 48 - 50 mpg to, at its lowest, about 38 MPG. Brought it back to dealer the other day who, after checking it out for two hours, did not acknowledge any problems, Since then, I have gotten from 50 to 55 MPG. Go figure.

5 of 5 people found this helpful.

My 2011 prius - had oil change synthetic as recommended, immediately my mpg dropped fro 50 to 47/47. I can't get it back to 50. What could cause that drop. Bill

35 of 35 people found this helpful.

I finally took my 2011 in for the recall last month. I went from 40 MPG (highway with a lead foot) to 33 MPG. Glad to see I'm not alone.

10 of 10 people found this helpful.

So what caused the big drop in mpg? My dealer suggested: increased ethanol in gas, low tire pressure, weather. He opposed an y possibility of computer problem. Suggested I buy my gas elsewhere, maybe mid-grade for a few fill-ups. I'm still bewildered. ,

4 of 4 people found this helpful.

I checked my oil last night and it looks like they put too much in when I took it in for the recall and oil change. Hopefully, the extra oil is the culprit. Hoping to make it to service today to get rid of the extra oil.

2 of 2 people found this helpful.

Our 2012 prius gas mileage dropped 8 to 10 miles per gallon after the recall also. It's not the gas it's not the oil, it's the software update.I drive 200 miles a day same route same speed and have the recall over a month now have a months worth of data I'm taking it back to the dealer.

6 of 6 people found this helpful.

I can say the same my 2012 prius has 99,000 miles on it. Before update 47.5 highway I run about 80mph After, no matter how I drive I can't get above 40. Defeats the purpose of the car with this milage. Had computer data and more, presented to dealer, they said there is nothing they can do. Even after acknowledging in writing the update may have affected my milage. I won't buy another one, that is for sure

5 of 5 people found this helpful.

Oh and I've tried everything. Non ethanol gas, k&n air filter, new tires, etc. None of it worked

2 of 2 people found this helpful.

My drop to 33 mpg turned out to be a combination of Firestone putting too much oil in during an oil change and they decided to underinflatey tires. After that, I started getting 40 mpg again. Are y'all using the dashboard's mpg or are you calculating it the old fashioned way?


Jimine I did it the old fashion way. Filled the tank 24.00 aka 10 gallons and drove it till 0 365 miles on the tank

2 of 2 people found this helpful.

Priuschat also ha a thread on this

1 of 1 people found this helpful.

I have a 2010 prius and up until the past 3 months I been getting 45-49 mpg. Tapered off to 42-45 mpg now im at 39. Car has 160k miles now. Checked the tire pressure F39 R34. I do my own oil changes 0-20 mobile 1 so I know that there is the right amount. Gas 89oct and didn't matter what brand of gas I used in the past. Wondering if it might have to do with the winter blend gas? Thing is I have never got below 42 with a roof carrier on top.

8 of 8 people found this helpful.

Anyone still on this thread? I just experienced this problem on my 2012 a couple of months ago. After I had read this thread I checked my oil and WHAT DO YOU KNOW it was overfull. I have been crazy and insanely busy with medical school stuff but have had some time to breathe recently and realized that I've been getting 44mpg at best if I limp the car around town. Just changed my oil today and will be hanging onto the fifth quart. The last business that changed my oil may have overfilled it. Tire pressure is fine. I have also read that my 12V battery may need to be replaced? Does anyone have any other suggestions? I also just replaced my air filter and plan on replacing my spark plugs soon. I'm moderately annoyed as I could achieve 48- 60mpg easily and I'm not sure I've hit 45 in a couple of months. I've also experienced five or six seizure like episodes with the car. I lost all power and there is no liner connection between the accelerator pedal and whatever kind of madness the planetary gear set and powerplant are doing. I'm assuming this relates to the recall aforementioned. I was not able to safely drive the car as it was violently lurching like an auto transmission was exiting your vehicle, so after restarting the car it fixed itself. I at first panicked and thought that I was losing my transmission. Have done the whole on and off again thing for the subsequent encounters. Super annoying actually. I'm looking to buy a Subaru soon!

3 of 3 people found this helpful.

The original tires are LR (low resistant) tires. I had some Uniroyal Tiger Paw tires put on to my Prius because the tire shop (Big O Tires) did not have any LR tires. I noticed immediately that my MPG had gone down. About a year later I looked at the Max Pressure of my Tiger Paws and noticed it was 44 PSI. Toyota recommends 35 PSI for the front tires and 33 PSI for the rear tires, but that's for the original LR tires. I decided to try a little experiment and increased the tire pressure to 40 PSI for the front tires and 38 PSI for the rear tires. Viola! My MPG immediately went back up to my original MPG. Hope this helps.

3 of 3 people found this helpful.

Make sure your tires are rated for 40 psi. Most passenger tires are not rated for that much pressure.

1 of 1 people found this helpful.

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