Why the sudden drop in our 2012 Prius gas mileage?

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.

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

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.

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. ,

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.

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.

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

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

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

Priuschat also ha a thread on this

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.

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!

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.

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

Brandon ( a year ago...so i know i'me just venting) i'm taking my V in today for three issues: the engine shuddering and clanking like the pistons want out of the block; gas mileage sucks since they replaced the engine (because the piston DID shoot out of the block; and the engine keeps burning oil beyond normal (8 qts in 3 months). would love to hear if anyone has any answers to any of the above issues.

I also have a prius V 2012 and finally did the recall last month. It was actually losing mileage before the recall too averaging around 38-40mpg. I know the rated mpg for the V is 42mpg, but when I bought it used with 33,000 miles, it was averaging 48-52mpg. That was 5 years ago. Had the spark plugs cleaned and the recall update, and no change. Still getting 37-40mpg depending on driving techniques, but never above 40mpg. Driving 800 miles every 2-3 weeks allows me to change my full synthetic oil every month. So it can't be the issue with oil. New battery auxillary battery aswell from Pepboys. Going to try some extreme things now like installing a small solar panel on the roof and small hydrogen generator in the air intake. That might give me 2-3 extra mpg.

happened to me last month on just oil change/ check on my 2012 V

I'm wondering if Battery Efficiency is a culprit. I'm good about my oil level and tire pressure. Even use the same tires for 7 years now. I heard that Tesla battery efficiency drops about 10% a year, and with no ICU engine to assist, this is easier to notice.

Mine is getting worse. With every refill of 9 gallons and up to 10 gallons max, I'm losing distance and mpg each time I hit up the pump. All the same station, same regular quality. I bought it with a average speed of 52 mpg at a range of 430 miles per tank back in 2013 around 30,000 miles. Its now at 33.5 mpg at a range of 361 miles per tank (10 gallons confirmed since at 10.5 the gas spills out). New auxillary battery, had my spark plugs cleaned, and new oil change. I might trade in for a mustang because those can get 35mpg. I'm losing faith in my prius.

You have to pay a lot of money to get good fuel economy. LOL

We have 135K on our 2010 Prius and now can get 39-40 MPG. Bought new and computer 'update' is most likely a scam to lower the MPG so you buy another, then Toy does another update to the trade to make it better again. My thoughts.

I have a 2013 Prius. MPG dropped from 52 to about 42-44. Changed gas, didn't help. Added octane booster, didn't help. Changed plugs, didn't help. Put 4 (about$100) cans of catalytic converter cleaner through the tank. Mileage increased back to about 52mpg for about 2 weeks then began to drop again. Now hovers about 44-46. I think problem may be in O2 sensors, but they are too expensive to change on a guess.

2012 Prius C Tire air pressure can make a big difference. Also air cleaner. Large battery air intake and fan blades need regular cleaning with a vacuum. Check battery terminals for corrosion.

Me too. My 2012 Prius for that mid 40s for years. I have 105,000 on it now. I’m getting mid 30s. No change to the tires, gas, oil. I’m wondering if the battery is wearing out.

Same here GuruGD3CD, but with 142K on the clock now. Also check your oil consumption, as the Prius eats oil after 100K!!

I am having same problem of lower gas mileage since the recall sw fixes. It appears to me like more gas is being used to charge the battery then previously used.

My 12 priusC is showing 34mpg instead of its normal 50 to52 mpg. BUT I just recently drove from Minnesota to Chicago with my buddy side by side in his 16 prius C making exact pit stops and his showed proper highway mileage. In fact hour fill ups were within cents of each other. Obviously im getting proper mpg but something is wrong in the reading or computer? Anyone have this problem? .

I am driving an 08 Prius and literally barely making 200 miles per tank of gas. Seriously annoyed.