Gen 3 Valve Seals - The Definitive Source of Oil Burning?

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by Pollymath, Sep 28, 2020.

  1. Pollymath

    Pollymath Junior Member

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    I know there are few people on this board who replaced their valve seals in an attempt to cure oil burning issues.

    My 2010 Prius burns oil like nobody's business. Like, a quart every 1000 miles. Maybe more.

    I've seen theories that this might be due to the coked up and carbonized "stuck" piston rings, but before I go blowing $75 on Valvoline Premium Blue Restore, I thought I'd check to see if the valve seals solved other peoples problems with oil burning.
     
  2. Pollymath

    Pollymath Junior Member

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  3. ASRDogman

    ASRDogman Senior Member

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    There has been non update, yet, of the few that have replaced there head gaskets and
    valve guide seal at the same time.
    I guess they have not put enough mileage on it yet.
    I personally believe the seals are the biggest cause from experience with other engines.

    I think we are all waiting to hear an update...
     
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  4. Pollymath

    Pollymath Junior Member

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    Any ability to squirt some sort of seal softner/conditioner directly on the valve seals, let it sit, and see if the oil consumption decreases afterwards? Even if it doesn't fix cracked/broken seals, it might be enough to identify the problem.

    Somewhere I noticed someone mentioned the relationship between the OCC and PCV. Like, if you OCC wasn't filling up, then maybe you had a PCV issue or vice versa. My OCC is very slow to fill up, despite burning 1qt every 800-1000 miles.
     
  5. ASRDogman

    ASRDogman Senior Member

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    Oil get sucked into the cylinder then burned.
    The seals get hard and brittle. Once they get hard, you can't soften them up.
    You just have to replace them.
     
  6. Pollymath

    Pollymath Junior Member

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    I know how valve seals works and why their failure burns oil.

    To be fair, that's the entire point of seal swell in high mileage oils.

    And, personally, I have seen results from products that claim to make seals more malleable, even once they've been dried and hardened. It doesn't restore them to new, but it does do something.

    Again, the point is merely to use it as a quick and easy determination. I don't want to replace the seals only to find them in excellent shape. It's a PITA process. Then again, by the time I squirt some wonder-lube on them, I'm half way to replacing them.


    I'm still curious if there is a relationship between OCC levels and PCV valve condition.
     
  7. ASRDogman

    ASRDogman Senior Member

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    I have water front property in south Florida really cheap if you're interested.....

    You are free to try whatever you want.
     
  8. Rebound

    Rebound Senior Member

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    The valves and the heads are machined to perfect tolerance to seal. It’s not about being soft or hard; it’s not some kind of gasket or soft material.

    MAYBE you can have some cooked-on deposits which prevent perfect seal. But considering the temperatures and pressure that cooks that stuff on, no magic oil is going to get rid of it.
     
  9. Pollymath

    Pollymath Junior Member

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    No I meant a top end oil of some sort. Essentially getting some sort of conditioner on the top side of the valves and letting it sit.

    Either way, seems like by the time Im that far into it I might as well go all the way.

    I’ll try thicker high-mileage oil, first.
     
  10. mikey_t

    mikey_t Active Member

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    Have you tried the BP treatment of 44K, EPR, and and MOA? They helped alleviate some of my 2010's oil burning after the first run, and I use the EPR/MOA with every oil change now, the 44K once a year.
     
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  11. Raytheeagle

    Raytheeagle Senior Member

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    Good to hear it is still working :).

    How many miles you up to now:whistle:?
     
  12. PriusTheGreenest

    PriusTheGreenest New Member

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    I'm in the market for a Gen 3 Prius. It appears the Gen 3 years 2010-2011 are the worst impacted years for poor seals/blown head gasket issue.

    Although it sounds like Gen 3 years 2012-2015 have less of this issue occurring, can anyone confirm if this issue was completely resolved for Gen 3 years 2012-2015 or just occurs less frequently?
     
  13. Mendel Leisk

    Mendel Leisk Sunday driver DIY’r

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    I doubt there's much difference. Sometime thru model year 2014 the pistons and rings were revised; that's all I've heard/gleaned. Oh, and EGR valve, and intake manifold had revs, at some point, but don't see that changing oil consumption.
     
  14. mikey_t

    mikey_t Active Member

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    I haven't driven much at all this year b/c of Covid, but I'm around 162k miles. I might switch over to 5W-30 oil at my next change though, as last time I checked it seemed like the burning was picking up again.
     
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  15. Pollymath

    Pollymath Junior Member

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    Bumping this back up.

    I just watched TheCarCareNut's Youtube video on his suggestions why the 2010-2013 Prius burns so much oil. He believes (as a Toyota Mechanic) that it's a case of overly long oil change intervals sludging up low tolerance pistons rings.

    If that's the case, then the valve seals shouldn't do much to fix this issue because the oil burning is from something else.

    If the "true" problem is the rings, then I'm back to thinking Valvoline Premium Blue Restore (the outrageously expensive Cummins sourced stuff) would probably help fix the issue with the rings, as that's what the oil is was designed to do. It's also why the BP Treatments likely give good results - those products are a consumer-grade attempt at doing the same thing VPBR was designed by chemical engineers and patented for.

    If people are changing out the valve seals on cars that are burning oil like nobodies business (like mine), and suddenly no more oil is being burnt, then I'd say TheCarCareNut's theory is bunk, and we should all save our time and money for a valve seal replacement.
     
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  16. Mendel Leisk

    Mendel Leisk Sunday driver DIY’r

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    Toyota thinks it’s pistons and rings, if you look up TSB168 and 169.
     
  17. ChapmanF

    ChapmanF Senior Member

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    Valve stem seals are a soft material, and replaceable.

    [​IMG]

    [​IMG]
     
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  18. ASRDogman

    ASRDogman Senior Member

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    If you watched the whole video, he also talked about the oil.
    He does make a good point for the OIL ring loosing tension. They are weaker so
    there is less pressure on the cylinder walls, which reduces friction and theorotically, improves
    fuel economy. This does make sense....except, today's cars use synthetic oil.
    It doesn't break down like conventional oil to cause the clogging. Yes, if you leave it in
    long enough, it will. But it's also designed to go 10,000 miles. The question is, is the filter?

    I do know for a fact, and experience, that valve guide seals fail and do allow oil to be sucked through
    the intake side.
    With weaker piston rings, and the egr cooler clogging up, and oil getting sucked in from the intake,
    which will produce a more "oily" exhaust to go through the cooler, it will cause more back pressure than normal and cause the head gasket to fail sooner.

    Will 5000 mile oil/filter changes stop, or slow this? Possibly. It certainly won't hurt, except in your wallet. :)
    Maybe split the difference at 7500....

    I also watched another video of the different viscousity of oil and what your "should" use, and why.


    Here are the videos:







     
  19. Mendel Leisk

    Mendel Leisk Sunday driver DIY’r

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    If you look at Fuelly mpg for various 3rd gen model year, there’s a slight but definite dip in mpg for 2015; I’d guess due to the higher tension piston rings.

    Toyota Prius MPG - Actual MPG from 8,314 Toyota Prius owners

    (^ Actually 2010 is a close second.)
    (And 2016 onward make a BIG improvement.)

    Toyota wanted to eke out a slight mpg improvement, for various reasons, presumably monetary. Similar story with the 10K oil change intervals.

    And their customers have to deal with the oil consumption.
     
    #19 Mendel Leisk, Jan 19, 2021 at 2:45 PM
    Last edited: Jan 19, 2021 at 2:51 PM
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  20. mikey_t

    mikey_t Active Member

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    It is an interesting video and makes me wonder where my engine is at. The first time I did the BG treatment with 44K, MOA, and EPR my oil consumption dropped dramatically. I've done it with every 5K oil change since. But now, a few years later, it seems to be back to burning around 1qt every 3000 miles. If I've driving through hills a lot it burns like there's no tomorrow. So if it was indeed the rings previously, it might be something else now like the valve seals or worn chamber walls. I just changed the oil last week so I'll see if it's changed or if it's just how my car is now.
     
    #20 mikey_t, Jan 19, 2021 at 6:41 PM
    Last edited: Jan 20, 2021 at 12:12 AM
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