First transmission oil change at 144K

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by indel, Jan 2, 2026 at 8:54 PM.

  1. indel

    indel Member

    Joined:
    Apr 1, 2024
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    Location:
    Northwest Indiana
    Vehicle:
    2012 Prius
    Model:
    Two


    As many of you know, I just bought my first Prius (2012 Two) a couple of months ago. Today, I did the first real service on it by changing the transmission oil. I was not prepared for the amount of work needed under the car and it ended up taking me nearly six hours to do everything. Here are a few observations:

    1. Raised vehicle on four jack stands in my garage and found that there was not enough space to work under the car. So I raised the front end again, which made the car slightly off level.

    2. When removing the engine under cover, a few clips broke and the box of new ones I purchased did not fit any of the positions, so that was a total waste of money.

    3. The old transmission oil was completely black. In comparison, I did transmission service on my 2006 Civic last week after 37K miles interval and the oil color was not very dark.

    4. I was able to drain about 3-1/3 quarts of oil. To fill new oil, a clear vinyl tube was routed from the engine compartment down towards the transmission housing. A small funnel was attached at the top. The first half quart went in pretty fast, after which it was a slog because of trapped air inside the tube. It took me a good 30 minutes to refill. Right around 3-1/3 quarts in, the drip from the fill hole started.

    5. The amount of oil that drained and refilled was less than what most of you have experienced. So I guess having the vehicle front angled up slightly does make a difference in both drain and refill. I found it hard to level the vehicle perfectly on the stands.

    6. Given the drained oil was so dark, does it make sense for me to drive 5-10K and then repeat the drain and refill? I can't believe the previous owner never bothered to change the transmission oil. The vehicle was serviced regularly at Toyota of Butte, Montana, and it was in their care until 136K, so I don't know why they never serviced the transmission.
     
  2. BiomedO1

    BiomedO1 Senior Member

    Joined:
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    Location:
    SacTown, Ca
    Vehicle:
    2021 Prius Prime
    Model:
    LE
    Toyota claims that ATF WS is a lifetime fluid - but I'm surprised the dealership didn't try to up-sell that.

    These transmission are planetary gear sets, so as long as they stay cool and something lubricates the needle bearings - they can go for a good long while. Changing the ATF every 60K to 100K actually puts you ahead of the game, since most people don't touch it. Some even argued that it was a SEALED unit, therefore unchangeable - strange how the service manual states to check it.:rolleyes::(:whistle:
     
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  3. indel

    indel Member

    Joined:
    Apr 1, 2024
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    Location:
    Northwest Indiana
    Vehicle:
    2012 Prius
    Model:
    Two
    Which presumably (according to toyota) ends as soon as the last of the warranties on the vehicle end.

    Here is an excerpt from the repair manual:


    (a) Add transaxle fluid until the fluid level is between 0 to 10 mm (0 to
    0.394 in.) from the bottom lip of the filler plug opening.
     Stop the vehicle on a flat road.
     Recheck the transaxle fluid level after driving when exchanging fluid.
     Insufficient or excessive amounts of transaxle fluid may be the cause of some trouble.

    So you are supposed to jack up the vehicle on a flat road somewhere during the test drive and check the level? Some of these directions in the repair manual are so nuts.