Significant Drop in Gas Mileage

@mikefocke 's 42 mpg average translates to 5.6 liters per 100 km. Now if that's year 'round, it's maybe 5.0 in summer, 6.2 in winter??

(To convert between the two systems, just divide either value into 235.2)

 

Fuelly will convert goodwitch's MPG to L/100km and says my lifetime is 5.6 and last 10 fill ups is 5.8. When I look at a graph of all my fill ups, other than obvious nozzle variations (high and next low or low and next high) they are remarkably consistent.

Thinking of my recent 10, those were winter and with more than normal cold days (golf course closed 18 days last month, for example). They were on newer tires (first 1000 miles) and at 40/38 pressures.

So maybe my impression was wrong and I'm not varying my usage and speed pattern as much as I thought.

 

Did you have the Inverter Motor/Generator TSB software reflash done?

 

I assume there was a similar TSB from Toyota Canada?

 

No idea how Canada handled it, but suspect the IMG issue crosses borders.

 

@mikefocke 's 42 mpg matches the original EPA combined rating. Here are the original and new ratings (US gallons) from fueleconomy.gov.

 

Read or search through the previouis posts on here. There are HUNDREDS of discussions about sudden changes in fuel mileage.

P.S. It is not necessary to keep repeating the story about your consistent "normal" use of the car. We get that.

 

SIGH. Looks like that is "normal" for THAT specific car and THAT specific driver(s) and THOSE usual traffic conditions.
There is no magic involved. The chart provided indicates that your usage is NOT that far from "normal".

I suggest that you tell your hubby that you are tired of hearing his complaints and maybe it's time for a new car.
Seriously.

AND IF YOUR HUBBY HAS "COMPLETE CONFIDENCE" IN HIS DEALER'S SERVICE DEPARTMENT........THEN WHY ARE YOU/WE WASTING OUR TIME WITH THIS DISCUSSION ??????

 

Yeah there was, well, for our 2010 regular Prius. Not sure about Prius v; at some point the cars started coming from the factory with the fix. But yeah, Toyota Canada was on it.

Oh, and: there was at least ONE report here, someone with a regular Prius IIRC: that post-fix the car's mpg plummeted...

FWIW, we had the fix, and the only thing noticeable was a slight increase in propensity to slip into electric-only propulsion. I'm definitely never lead-footing, so never noticed a fall-off in acceleration.

 

I'm sure I have no suggestion.
There is a finite number of factors that can affect gas mileage.

If one is supremely confident that it absolutely can NOT be...
The fuel itself.
Environmental Change.
The Maintenance or mechanical state of the vehicle. (Including Batteries and Hybrid Components)
Or the driving habits or action of the user..

Then by default there is nothing else left.

Best of Luck.

 

I have an old 2004 Prius with 220,000 miles on it. I have also noticed lower fuel mileage over several years now, Several factors contribute to the drop. Fuel may be the culprit, but that is hard to corroborate. The winter cold really causes a significant drop in fuel mileage.
I know that running the fan causes the EV mode to degrade and cause fuel mileage drop. If you crank up the fan the EV mode won't engage unless the engine is fully warm.Try turning the fan off for several miles to save fuel.

Here is the biggest culprit, in my opinion, is the Traction Battery. This battery slowly degrades over time and the result is a decreased volume of electricity. This means that the accelerating capability of the battery/motor is diminished. Now your gas motor has to work much harder to accelerate the car, plus more energy needed to charge the battery.

I am waiting for the battery to die and I'll have to repair it. I haven't spent 400 bucks for a grid charger either. So far the battery is hangin' in there.

My VCI won't connect with the car anymore so I don't know how bad the battery has gotten.

 

When our car is partially warmed up, at red lights, I can reliably turn the engine off/on, by either turning the cabin temperature setting lower (say from around 22C to 18C), or just turning the system right off. Once the car's fully warmed it'll shut off anyway, but it's definitely a factor.

 

If it was my car, I'd want to check the 12v battery, then I would clean the MAF sensor. I recently did this on my car and saw an immediate improvement...

It also occurs to me - would the car throw a code if the coolant thermostat became stuck open, such that the engine was over-cooled??

 

Just came across your concern about L/100km and just wanted to chime in as i have noticed a similar spike, i have a 2012 Prius V and live east of Toronto. I drove roughly 80km into Brampton every day, and I've noticed in the winter i get around 7.0L/km. My car just past 380,000km and still runs like a dream, but like many other people have pointed out there can be so many different factors such as fuel isn't what it used to be with different additives, tire compounds can also change without people being aware, evening when using the same brand. In the summer months i see a drop in fuel economy with my summer tires and warmer temps being a little easier on the engine.
Also over the years the engine starts to wear out from the inside and auto makers generally state what the fuel economy is, which are not always true..it's hard to pin point what the culprit is exactly because there are so many factors not in our control.

I know it's been a few years since this post has been active, but have you check the intake filter making sure the air/flow mixture is correct. Cause with less air going into the engine it could burn more fuel. Or even dirty injectors, or old ignition coils and spark plugs...old fuel pump..I'm going to be watching the difference in the next couple weeks as we are slowly transitioning into spring like weather and winter tires can off

 

The engine controller takes care of that, so it should get the correct air/fuel mixture nearly all the time. When less air gets in, the controller adjusts the fuel to still get the correct mixture, and efficiency should remain unchanged, though maximum available power will decrease.

 

After reading this thread and noticed no here has mentioned or put together on one reply.
1. Your 2012 Prius V is 10 years old.
2. You live in Canada and have long cold winters. All Prius models have poor gas mileage during winter months. Did you notice poor gas MPG only during winter cold days. In other words did you have a longer winter this year during your mpg tracking?
3. The age of car and colder weather diminishes the Prius MPG dramatically from Summer MPG vs Winter MPG.
4. Hybrid battery is good up 100k-150k U.S. miles because I don't know KM. The age of hybrid battery is definitely a factor. As the Hybrid battery ages it becomes less efficient. Which means lower MPG.
Secondly 12 volt battery is getting old too and not maintaining a good charge can effect gas mileage as well. The 12 volt may turn the car on but never reaches max charge because of age. They usually last about 5 years for OEM truestart Toyota 84 month battery in extreme weather regions such as Canada. They tend to last longer in mild weather climate conditions and people who uses their car everyday vs people that don't drive much. I hear very often because of Covid that people didn't drive there cars for months and 12 volt died.
5. My friend who live in Montreal had to change to winter tires by law or would tickets if his car didn't uses winter tires. Those tires have softer rubber which can reduce the Prius MPG.
6. Any mods can affect the MPG on the Prius.
Remember the car was designed to have very little drag. I put a roof racks on my Prius and it lost 3 mpg for highway driving 70-80 mph. Installing a hitch and running bike racks or hitch carriers can affect mpgs too.
*******Unintentionally mods accidents, dents, driving around with snow pack on roof and hood can affect MPG. Another issue people don't inspect is the plastic under armor under the car and wheel well. These get damaged and cause air drag and drops MPG.
7. Maintenance is another factor to keeping good MPG. Do you change oil on time and replaced engine air filters every oil change? If your air filter gets clogged because of dirt roads or tons of leaves. That reduce MPG dramatically as well.
My guess is your Prius is getting old and reduce MPG is expected problem of aging car issue.
How miles or KM do you have on the Prius?
Do you have a good maintenance record?


SM-A526U ?

 

I have a 2014 Prius V that had the P0301 engine code. I had my mechanic replace the spark plugs and coils, Still had the code so he flushed the EGR piping with carburetor cleaner and something was cleaned with Mass Air Flow cleaner. The shudder is gone but my MPG dropped from 40-41 to 35.4. Help, what is happening?

 

how are you measuring mpg's?

 

How many miles on it?

a long neglected EGR system will lead to head gasket failure, typically starting at cylinder one. EGR cleaning is never a bad idea, but once head gasket fails EGR cleaning won’t “heal” the head gasket; you need to address that first. Leak down test and boroscope inspection is good for head gasket diagnosis.

 

I am measuring MPGs with the display. I always reset the avg mpg after each fill-up.

almost 180,000.