36 MPG City & 50 MPG Highway

Are there any codes?

 

If your Prius was first sold in California and is currently registered in California, you are covered for 10 years/150,000 miles under the CARB warranty.


As for your mpg drop - it could be the battery. It might also be that you're using the AC a lot more and doing short city trips. Did you own the car last summer and drive the same?

 

Did you replace the 12v battery before the drop in mpg?

 

How many miles on it? Any maintenance done around the time of the mpg drop? Recent tire replacement?

 

Dr Prius smart phone app is a popular one. You need an OBD Bluetooth adapter, Carista is good. Cost is $5~10 for full functionality IIRC.

 

You can read two posts I have about a Low MPG Mechanism that affects only City Driving and not Highway Driving.

Low MPG Mechanism Post.

Screenshots of others affected by this Low MPG Mechanism

Here is a brief explanation of the post:

Basically what happens is after a 12v disconnect... certain parameters are reset in the ECU's that tell the Prius to use EV Mode aggressively. Because of this the Prius will run the gas engine much more frequently in place of using EV Mode at City Speeds... causing a 5-10+ drop in City MPG's and resulting in what I call the WEAK EV State. Highway MPG's are not effected nor is total power output effected... only how the Prius decides to deliver that power using either the Combustion Engine or Electric Motor (MG2) at city speeds.

What appears to initiate the Prius back to the MAX EV State (where EV Mode is used aggressively again + good City MPG's) is a consistent low stress highway commute for multiple drive cycles in a row... During these highway commutes... the Prius appears to check certain parameters and calculations... and once all the conditions are met that the ECU's are looking for... the MAX EV State re-initiates and the Prius then will stay permanently in the MAX EV State until another 12v disconnect or ECU reset.

But I do not know the exacts of this process. Toyota (except maybe a few engineers that designed the Prius) and nobody else knows exactly why this happens. I am the first one to flesh this out in my post. The Prius can become permanently stuck in the WEAK EV State... Mine has been stuck this way for 3+ years now.

It doesn't sound exactly like what's causing your low mpg because a 12v disconnect didn't precipitate it... but the low city mpg, good highway mpg does sound very similar.

Posted via the PriusChat mobile app.

 

I am getting rusty, but I do not think we have had many Gen3 with HV batt issues at 8-yrs and 85k miles in the USA.

For the older Gen2, the early batt death was a little more common, because Gen2 had the issue, if you ran out of gas, the HV batt could deplete fully, which is not good for the HV battery. Gen3 fixed that issue by not allowing full depletion of the HV battery upon empty fuel tank.

Another unusual scenario I seem to recall, if every day you have the same drive; eg; up a hill to work to deplete the battery and then park in hot sun all day, that was not a good scenario.

I am thinking Gen3 has 10/150 in Ca. for the HV Batt.

 

I routinely disconnect the 12 volt whenever doing brake maintenance, 3 times now, and never noticed a mpg drop. The engine does an odd rev up for the next few start ups, recalibrating something, but seems like it’s through that process very quickly, with no side effects.

 

When I replaced the 12v battery I didn't have any problems. I still got an average
of 38mpg in the city.

 

Some items on cars, such as error codes, and certain Prius TPMS behavior (recognition of stale reading from the sensors) do require 20-30 minute drive after a reset. For example (on Gen2 anyways) you can reset the TPMS codes to bogus numbers to temporarily turn off the TPMS warning light. If you only ever take short drives, 5 to 10-minutes per trip, you can actually go a long time before the you finally take a longer trip and the car finally has enough time to realize you put in bogus codes, and then the TPMS light comes on.

So it makes some sense to me there could be something to the story above, but I had never noticed it. Not to mention getting into Stage5 on the hybrid system is a step process, and detailed in older Gen2 posts.

 

I know this is a late reply... but you only get 38mpg city? That is awfully low. You should be getting around the EPA estimate of 48 mpg for Gen 2 or 51 for Gen 3.

You may actually be a Prius owner that is chronically affected by the low mpg mechanism I linked if you are only averaging 38 city driving. You should be averaging much higher.

Working on a video now to describe the low mpg mechanism I've discovered more concisely.

I just updated my initial Post with a condensed explanation of what I'm talking about: https://priuschat.com/index.php?posts/3303871

 

"low mpg mechanism"????? That's not a real thing.
The reason for the supposive low mileage is because of realizm.
It's stop and slow and stop and slow etc. I'm VERY happy with 38mpg.
My van was 16mpg.

I can get better, if no one else is on the rode. But I'm not going to "ease" away from a
stop sign or stop light with people behind me. So with so many stops, and cars,
38 is great!

There is NO way any vehicle will get better mileage in a city than on the highway.
Unless you have the "Prime" that can run longer and faster on the battery.

 

Have you heard of the EPA and its fuel mileage numbers?
How do you explain this?

 

This is absolutely false and why the EPA estimates for City MPG of the Prius are rated at higher City than Highway.

The EPA tests are very realistic to real world driving and why they were implemented so car manufacturers can't jumble the numbers through unrealistic tests.

The EPA MPG Tests include everything from AC use and various scenarios/styles of driving to come to the conclusions that they do. They are highly accurate to how a car should perform real-world MPG wise.

By Low MPG Mechanism... I am referring to my post here: https://priuschat.com/index.php?threads/229166/

Basically it surmises a previously unknown mechanism of low mpg based upon how the Hybrid Control ECU dictates the useage of EV Mode.

If you would like to see other posts of Prius owners being affected by this exact same Low mpg mechanism I speak of.... Here is a link to screenshots of Prius owners who are affected by this same low mpg mechanism I speak of.

Currently I am working on a video to describe what I'm talking about concisely. I hope to have the video done before the new year:

 

ha ha ha You actually believe the epa???? It's all about money for them.
They do calculations, not actual driving.

I've spoken with other Prius owners I see fueling up, and it's the same for them.
As I said... "It's stop and slow and stop and slow etc.".
I also said: "
I can get better, if no one else is on the rode. But I'm not going to "ease" away from a
stop sign or stop light with people behind me." Because where I'm from, you could get shot
for doing that crap.

Under "ideal" conditions, maybe. But in the REAL world, no.
The epa is absolutely false. And remember, they say "estimates" not REAL.

You can go on believing that stuff, it's your like.
I don't waste my time with it.

 

Lol...

The EPA is extremely stringent with it's testing methods so yes I do. It is highly accurate to real world driving.

Yeah... EPA estimates are based on real world driving. They are highly accurate. Watch the video above... You'll see what I mean

If you were in a MAX EV State Prius as I describe in my Low MPG Mechanism... you could easily accelerate aggressively in EV Mode up to 40mph down to 3 of 8 charge bars on the display... keeping your City MPG's close to the EPA estimated of 50ish.

But you too are likely affected by the phantom low mpg mechanism I talk about in my post... or as I call it... The WEAK EV State.

 

Oh gees, stop beating the poor dead horse!!!
Find something better to do with your life!!!!!

The epa should be shut down and they should all be in jail.