2015 Prius on replacement battery not getting good mpg

2nd replacement? So you got a used battery? Never worth it.
You need the Sodium Ion NEW battery pack.

Never heard of that brand of tire. Tires are important to fuel mileage.
What tire pressures are you running?

Both will highly effect mpg. Cooler weather effect mpg also.

 

Are these battery replacements OEM? Were they replaced by the dealership? Post some results from Dr. Prius app or Hybrid Assistant.

 

Just to clarify: you replaced the hybrid battery, or 12 volt battery?

Off-topic, but if you haven’t: I would clean the EGR (Exhaust Gas Recirculation) system as soon as possible, and replace engine water pump and thermostat.

 

So, what do the tires have to do with it?
You did something, battery, tires, both at the same time? Correlation to cause and effect?
This is actual mpg, miles/gals, full tank?

 

Are these Toyota guess-o-meter numbers or manually calculated tank to tank averages.

It's been pretty cold and rainy in Redding and we know how weather affects these cars. Unless you do an apple to apples comparison, under the same circumstances by adjusting only ONE variable - it's difficult to make general comparisons.

 

I thought I just said that.

 

I was typing when you hit the return key to post your response..... so I didn't see it.

 

I thought you had me on ignore, or something.

 

I'd bet the oem hybrid battery had been sitting a long time, and the charge was low.
That's really bad. 2 bad batteries? I take it they are used blocks, not new.
You should tell them you want NEW blocks, not "refurbished/used" one.

There is nothing wrong with the Sodium Ion battery. There are "those" that just like to argue and
will complain about everything they can to pull others into their sad life they choose to live.

I installed mine in September 2024. I've had NO issues. And this recent cold weather, it performed perfectly.
It held the charge, and the discharge/charge cycles were the same in the cold as the heat.

Tires make a big difference. You should get the ones that are designed for hybrids.
I'm currently running the Hankook Kinergy PT (H737) tires and average 48mpg, without trying.
And of course the Sodium Ion battery really helps the mpg.

Toyota recommend 36 front and 32 rear. I run 38psi front and rear. Some run higher, but they the
risk of over inflating then overheating could cause a tire failure.

 

Unless you are talking about 'labor' at local dealership being overpriced, it makes no sense. I can't imagine a local hybrid shop giving you a brand new OEM for much lower price than the list price. So what did they give you exactly? Did you check receipts and did you get a toyota warranty documentation? Also, Toyota only gives 12 month warranty on batteries sold over the counter. The 3 year warranty is only when the dealership installs the battery.

 

No.

With 150k and untouched EGR, head gasket failure is likely to happen, sooner than later.