Valve seals or oil control rings? Which most likely?

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Doug_M, Aug 6, 2026 at 3:09 PM.

  1. Doug_M

    Doug_M Junior Member

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    Location:
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    Vehicle:
    2009 Prius
    Model:
    Two
    My 2009 is consuming oil, about a quart every 1500 miles or so. The car has 250k miles. I have replaced the PCV valve to no effect.

    If it is the seals I might just persuade myself to replace them... I am planning to look in the cylinders with a borescope to see if they are glazed, in which case I won't bother.

    I did try a piston soak a while back, but I might try it again with a longer soak. How effective is a Chemtool soak? If that makes no difference does it very strongly indicate valve seals, or is it hard to say?

    Are there any other diagnostics than might be reliable?

    Thx.
     
    #1 Doug_M, Aug 6, 2026 at 3:09 PM
  2. BiomedO1

    BiomedO1 Senior Member

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    More than likely the piston low tension oil control rings. A piston soak is simply a "hail mary"' because it doesn't address the actual issue. It's only going to be a stop-gap measure; if it works.
    The other issue or future issue is that high oil consumption is going to kill the CAT; eventually.

    I would start saving for another engine - NOT a used one. That's gambling and I don't consider tossing $3K+ at a used engine with KNOWN defects - probably ending up in the same place in a year or two. Or sell it.

    Just my 2-cents
     
    #2 BiomedO1, Aug 6, 2026 at 3:33 PM
  3. Brian1954

    Brian1954 Senior Member

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    Model:
    III
    The Gen 2 engines do not have the low tension rings. The low tension rings started in 2010 Gen 3 engines.


    Posted via the PriusChat mobile app.
     
    #3 Brian1954, Aug 6, 2026 at 4:13 PM
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