[calvinmckenzie]

Over the past 7-8 months, my MPG has gone from about 38 to less than 32. I fill up from the same stations, and my driving habits have not changed. The decrease has been gradual, going down to 36 for a while, then 34, and now 32 or less. I have contacted my dealer to see what kind of testing they can do to see if the battery is failing or just losing capacity. I'm checking to see if anyone has any advice. I have 88K miles, so the Toyota warranty should still cover it.

 

[Tsonder305]

Haha, I was literally about to start the exact same thread. Same for me! I have a 2018 hybrid limited (so it's the bigger wheels, which lowers the MPG somewhat) but I've noticed a decrease too. I have around 56,000 miles. The drop off seems more pronounced for local driving, which is why I thought it might be the traction battery. And I don't rely on the MPG gauge in the car, I record the odometer readings between fill-ups, and divide by the numbers of gallons the car takes, so I know the drop off has been real.

I'd also like to know how to do the test, and if so, what is the process for getting it repaired or replaced under warranty.

Any advice would be appreciated!.

 

[Variman]

I have read over at Prius chat that a failing 12 volt aux battery can affect MPG. I would first check the air filter and tire pressure. If these check out, have the 12 volt aux battery tested.

 

[Tora-Awdi]

I have a 2017 hybrid limited with 375K and starting around 100K the mpg began to deflate from ~38mpg to ~30mpg at around 250K. It has pretty much settled in at this number since. I am still running all original HV cells and 12V. The HV pack I monitor with Dr. Prius and they currently test at just below 50% battery life so I am sure this is dragging the mpg down and hope for a boost when I finally replace the HV pack. Changing the 12V seems like a less expensive attempt at improvement, has anyone done this to any effect?

 

[WDC1]

Friend has a Ford hybrid and mileage dropping. Found out ford automatically tells the battery to slow down after so many years so it can be replaced. My friend found the needed software and loaded it into the car and reset timer on battery. Yes, weird but it worked for him. I think he had well over 100,000 miles.

 

[WDC1]

Oh, it was all on google.

 

[jrohland]

That is a large drop in fuel effiency. I would recommend you check the high voltage ( a.k.a. traction ) battery.

If you see my post here:
Rav4 Hybrid Torque Pro PIDs | Toyota RAV4 Forums (rav4world.com)
I set an app on my phone to check the battery blocks. If they are about the same voltage and internal resistance accross all 17 blocks, the battery is likely fine.

 

[Tsonder305]

I have been following it, my Rav4 has gone from getting consistently 32-33 to 28-29 (and I'm not going based on the car's measurement, but based on fillups and odometer readings. I have not changed driving habits and my tires are new and recently aligned.

Besides jrohland's suggestion to check the traction battery (which I don't know if I can do), anyone have any other suggestions?