2010 Prius III MPG Loss - Experts - No Joes Please!

I also vote for a faulty temperature sensor. Your symptoms are the same of having an overheated battery like what was happened to many owners in the last very hot summer. Some diagnosis could be made just with and android phone with Torque and a bluetooth odb adapter.

Inviato dal mio GT-N7000 utilizzando Tapatalk

 

i sense that most, if not all of these answers are from joe's.

 

Not to clog the thread but is the oil level at full or under? I had a dealer in Socal overfill it once and only noticed when my MPG dropped from 53-55 to 45-50. The engine would run longer as well and at odd times when it should have been off, who knows if that was from increased temp/pressure...

 

The Prius has a great feature that might help diagnose this problem - the 5 min / 1 min interval fuel economy reading. Knowing what mpg your car is getting in highway conditions would tell if it's likely an engine/fluid/aux battery issue or (what I suspect - a loose/dirty connection issue) - i.e. nothing to do with the traction battery. Likewise, knowing what mpg the car gets during "city" driving might point the finger at a hybrid battery-related issue. Can you post those numbers with associated description, please?

 

Additionally, you can use the techstream software in live data mode to detect unusual values. I'd be happy to compare my values with yours.

 

I'm a Joe (Actually a David), I'm really troubled by the fact that the car is firing up the engine and the engine isn't turning off. That is what I would want to pursue. The engine running too much will kill MPGs especially at the high MPG's we get with our cars.

Thank you for your very thorough post! I hope that things work out for you.

 

Wanted to comment that I experience a similar loss in MPG everytime after a 12v battery disconnect on my Gen 2 Prius until the ECU's relearn.

The fact that this happened directly after some major maintenance, some of which included working on Spark Plugs, signals to me that the 12v was probably disconnected as per procedure.

The chances of me getting a reply are slim, but do you know if the mechanic disconnected the battery? If they, did your MPG loss was likely a result of resetting the ECU's. The relearn parameters to return to nominal efficiency will NEVER happen under certain driving circumstances.

It can be rather tricky to get the Hybrid ECU's to relearn. It seems to require several jaunts of freeway driving around 70+ MPH.

But once the Hybrid ECU relearns, it's behavior does not change again until a 12v disconnect.

This phenomenon as I've experienced it is described here:



Hybrid System Less Efficient After 12V Disconnect/Battery Change? ECU's?

There is no other post on PriusChat that describes this phenomenon in detail besides my post. I am assembling a list of posts where this phenomenon could be applied. I hope to potentially get an answer as to what are the exact relearn parameters to return our Prii to max efficiency after a 12V dissconnect.


Posted via the PriusChat mobile app.

 

I disconnect 12 volt whenever doing brake work. I’ve found the subsequent 2~3 start ups, there’s a strange rev up that happens, as if something is being calibrated.

 

What about in terms of MPG? Do you notice loss of EV power for a sustained period?

What is your average MPG and commute normally?

Posted via the PriusChat mobile app.

 

No appreciable mpg change. Lifetime fuel economy currently at 5.0 litre per 100 kms (in sig). Translates to 47 mpg US.

 

Have you ever had any dealership ECU calibrations done?

Posted via the PriusChat mobile app.

 

Don’t think so. I’ve had software update to protect inverter, that’s it as far as I know.

 

I'm not an expert but a newbie and asking about the software update
And always expect a bit lower mpg after each transmission fluid change

Posted via the PriusChat mobile app.

 

I had a bunch of ideas, but, frankly you sound lile a pompous wank, so, good luck.

 

WHY would you loose mpg's after changing the trans fluid? There would be no logical reason for that to happen.
Or are you just asking about it?

 

It's a simple theory, if a working mechanism works well, that means everything gets on well each other. Once you change smt out of it, that ll take some time to get used to as they used to ... The longer intervals, the higher changes
Also I m guessing CVT takes a role to get a mpg like 55


Posted via the PriusChat mobile app.

 

That's a simple theory all right. And just as there are surely situations where it could turn out to apply (say, fuel injectors with trim being learned over time by an ECM), there are just as surely situations where it doesn't.

 

Good grief. The Op posted twice in 2015 and has not been here since. He probably took his then five year old gen3 back to the dealer and they found the disconnected temperature sensor or the hv battery died the next day.