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5 Reasons Your Toyota Prius Is Getting Awful Fuel Mileage

Has your Toyota Prius lost some MPG? Well, you are not alone. Here are 5 reasons why you are getting bad fuel economy, and what you can do about it.

So, your Toyota Prius has lost 5 miles per gallon, and now you are wondering what to do about it? Well, never fear you are not the only one who has dropped some serious mpg.

This article will discuss what can cause a drop in miles per gallon and what you can do about restoring it.

Hey, Did You Check The Weather?
Believe it or not, the number one reason Prius owners see a decrease in fuel economy is inclement weather. That means extreme hot or extreme cold (like we are seeing now) plays a massive role in your Prius's efficiency.

Toyota Prius MFD

In cold situations, plaguing so many owners right now, the gas engine has to run to make the heater work. If you are running the gas engine, you are using gas.

You could bundle up, drop the thermostat down to 70 and go about your business, but chances are you may only gain 1 to 2 mpg. My honest opinion is that you just need to tough it out for a month. Once the sky turns blue again, and all the ice is gone, your car should bounce right back.

Those Round Things Are Called Tires
Tire pressure, the silent mpg killer. Check your pressure every month. I do not care if the light is off or not. If you care about fuel economy you will check your pressure.

Toyota Prius tire chains

The recommended pressure found inside the driver door jam is a starting point. That 32 psi is a decent balance between ride quality and fuel economy.

If you want to boost your econ, take your psi up a bit. The extra pressure will allow for less drag on the road resulting in a better economy. I do not recommend higher pressure in the winter though, you need all the grip you can get. A suitable set of snow tires is the best bet for winter.

Hey, That Is A Cool Battery
Your aging hybrid battery could be costing your Prius to have a lower econ. A failing or bad battery does not allow for adequate gasoline engine off time. This action results in more extended periods of engine run time and lowers fuel economy.

Toyota Prius charging HV battery

A smart Prius driver knows that periodic reconditioning will help mitigate this issue. Once or twice a year, give your hybrid battery some love. It will treat you right for longer than you would expect. To learn more about battery reconditioning, check this article out here.

Do You Remember When?
Ever been so busy in life that you completely forgot to take care of your car? I have. The washing, oil changes, tire rotations, and everything in between are all part of fuel economy.

When we forget to service our Prius, this can lead to components breaking down and causing the car to drive poorly. Typically, a vehicle that does not operate well will also be one that drinks more fuel.

Toyota Prius Spark Plugs

Part of keeping clean also means a clean fuel system. Injectors, air filters, and spark plugs all need to be taken care of. Keep that Prius humming with regular maintenance. You will be glad you did when you get 45 mpg or better.

Pay No Mind To That Light On Your Dash
Trouble codes are more than just a little annoying light on your dash. They mean there is a system fault. When the car is not operating correctly, how do you expect it to get good mileage?

Toyota Prius Check Engine LightWhile some trouble codes are far more severe than others, keeping the light off means your car can learn values to help it sip fuel rather than gulp it. If you ever get a check engine light, be sure to have it checked out as soon as possible and get the proper repair done. Your gas tank will thank you.

That is all for this one, folks. If you have any questions, you know where to find me. Have questions about whether to install an oil catch can or not on your Prius? Take a look here to read about it.

Take a look at how history is repeating itself with Telsa.

Check out this wild new battery tech that Tesla has and why it will forever change the auto industry.

Peter Neilson is an automotive consultant specializing in electric cars and hybrid battery technologies. He holds a Bachelor of Science in Automotive Service Technology from Weber State University. Peter can be reached on Linkedin and you can tweet him at The_hybrid_guy on Twitter. Find his page on Facebook at Certified Auto Consulting. Read more of Peter's stories at Toyota news coverage on Torque News. Search Toyota Prius Torque News for more in depth Prius coverage from our reporters.


Michael (not verified)    February 17, 2021 - 11:01AM

I was down 5-6 mpg and did a fuel system clean, no change. Then I cleaned the mass flow sensor and immediately got 4-5 back.

Don (not verified)    June 16, 2021 - 2:51PM

The mileage has been declining significantly 2007 Prius. Car seemed to be running fine, just poor gas mileage. Since plugs were supposed to be good for 100k miles I didn't connect that was what the problem was. When I removed the NGK iridium plugs I could not believe how much they were worn. I'm really also surprised that the performance was not affected, just the gas mileage. I replaced with Denso iridium and now I'm getting 10 more MPG'S. Hope they are better quality and any future decline in gas mileage I will be checking my spark plugs first.

John (not verified)    September 8, 2021 - 12:36PM

In reply to by Don (not verified)

My 07 was getting poor mileage so we checked the plugs and same deal, they were incredibly worn out. Just got them replaced and will clean the MAF sensor as well and see what happens!

Lesley (not verified)    February 25, 2022 - 7:15AM

In reply to by Don (not verified)

My 2007 Prius was getting 450mp tank full now I’m down to barely 300mp tank full .. I regularly get oil changes, tire rotation, balancing etc . I have I’ve 240,000 miles on my car what else should I do .. and when does the transmission need to be serviced the dealer is saying 300,000 mile point.

Karl W Neiswender (not verified)    March 15, 2022 - 6:04PM

In reply to by Lesley (not verified)

You really need to compute MPG, not by the tank.
Each fill up may differ in the amount of gas put in.
Using miles per tank will give you numbers with a large degree of error.

Archie Grey (not verified)    November 7, 2021 - 7:31AM

What would be considered poor mileage in a Prius? I was looking at a used one that got 27 mpg with 75 miles driven at an average of 12 mph. Does that seem like something is wrong?

Bob (not verified)    July 30, 2023 - 1:56PM

In reply to by Archie Grey (not verified)

Hi Archie,
So you question, "Is 27 mpg poor for a Prius that went 75 miles driven at an average of 12 mph?"
Lemme see... It looks like that 75 mile trip took over six hours. (75 miles/12 mph = 6.25 hrs) - That means the Prius did little more than idle its motor for 75 miles and it still got 27 mpg (Calculated by the 'puter, I presume.)
Before I give your answer, I'd like to suggest you take your fool head out of your rectum. - The world might look and smell somewhat different.

Archie Grey (not verified)    November 7, 2021 - 7:32AM

What would be considered poor mileage in a Prius? I was looking at a used one that got 27 mpg with 75 miles driven at an average of 12 mph. Does that seem like something is wrong?

John (not verified)    November 8, 2021 - 12:41PM

In reply to by Archie Grey (not verified)

What year is it? A 12mph average is barely even moving so I have no idea what the owner was doing to average that over 75 miles...but 27mpg is awful in a prius. I have never gotten anywhere near that after 5-10 miles of driving on a new tank. Any MPG in the low 40s and below, if you arent climbing hills all the time, is lower than it should be. I'd be worried that the battery is on its last legs and barely helping out to get that bad of an average over 75 miles. I would probably steer clear unless they are selling it incredibly cheap.

ed oneill (not verified)    December 11, 2021 - 12:00PM

2021 prius prime was giving 30 miles on full charge and I could drive all the way to work on charge only with in 3 weeks it systematically went down to 22 and do not get any where near work on a charge driving same path no heat no lights toyota says nothing is wrong

marc casden (not verified)    December 30, 2021 - 10:00AM

i put in a brand new Toyota hybrid battery, changed my spark plugs, cleaned out the throttle valve and the air flow sensor. my first fill up after all that and im still only getting 28 mpg. What is wrong

Kcsaxton (not verified)    February 3, 2022 - 4:04PM

In reply to by marc casden (not verified)

Are you putting your foot in it? I can drive my prius at 45 miles per hour and my husband can do the same on the same route, etc. Until you learn to pull back on the gas when the car is at the speed you want, you'll get poor gas mileage. It's a bit of a balancing act - use cruise control when you can and this should help as well. The mpg meter will help you learn to drive efficiently

Marc casden (not verified)    February 22, 2022 - 6:01AM

I put in brand new toyota hybrid batteries , spark plugs. Cleaned out throttle valve and I'm only getting 37 mpg. I drive the car easy the tires are inflated. Why am I still getting poor gas mileage

Deb (not verified)    April 21, 2022 - 11:27PM

I am only getting 28 mpg on my Prius 2010 with only 96k miles. I got 51 mpg first fill up, then 47, then 37 and now 28. I just purchased it 3/11/2022. They said they gave it a complete diagnostic.

David Hackett (not verified)    August 7, 2022 - 8:40AM

My 2013 Prius V was getting a consistent 43.9 mpg until a few months back. Now I am getting 33.4 mpg, but my vehicle seems to run fine. Could it be that there is now more ethanol in the gasoline, which presumably will cut back on the mpg?