Excessive oil consumption explained and how to fix it

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by Peter123, May 31, 2019.

  1. Peter123

    Peter123 Member

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    THE PROBLEM
    The Prius uses a high-efficiency Atkinson cycle engine rather than the usual high-power Otto cycle engine. A drawback of the Atkinson cycle is that you can get very high engine temperatures. Toyota recirculates cooled exhaust gas from the exhaust manifold to the intake manifold through the EGR valve to control the combustion temperature. In older cars the EGR cooler plugs up. And, the engine starts to run a lot hotter. Then we see deposits forming in the engine plugging up the piston rings and the intake and exhaust valves. The degraded piston rings then leak oil into the engine where it burns off. With time you will also see spark plug tips eroded and eventually the head gasket will fail. Toyota's solution at this point is to replace the engine. If you catch it fast enough you can avoid that expense.

    THE SOLUTION
    The fix comes in three parts. Cleaning out the EGR system. Cleaning the piston rings from the oil fed side. And cleaning the combustion chamber, which includes the part of the piston rings that face the combustion chamber.
    1) Cleaning out the EGR system. This is covered very well by nuts about bolts in his video. So I will not go over it here, but I will point you to his posted list of videos.
    Nutz About Bolts Prius Maintenance Videos | PriusChat
    2) Cleaning the piston rings from the oil fed side. This can be done as part of an oil change. Use Motor Flush on an oil change. Follow the manufacturer's instructions. Once you see what a difference this makes, you may want to do it a second time.
    Here is the manufacturer's link
    Motor Medic | Motor Flush | Get More Out With Every Oil Change
    3) Cleaning the combustion chamber. I used Cataclean, which is a very effective engine cleaner. It was designed to clean catalytic converters. It cleans out everything. I have heard some people use Seafoam. You can try that, but at usable concentrations it tends to stink up your entire street. Whichever you use please follow the manufacturer's instructions
    Here is the manufacturer's link for Cataclean
    Cataclean - Fuel & Exhaust System Cleaner
    and for Seafoam
    Sea Foam | Makers of Sea Foam Motor Treatment & other engine products
     
    #1 Peter123, May 31, 2019
    Last edited: Jun 1, 2019
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  2. Merkey

    Merkey Member

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    Does it make sense that a cleaner exhaust gas would result in fewer deposits in the EGR system? If so, then how would one produce a cleaner exhaust.
     
  3. Grit

    Grit Senior Member

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    Yay! Another oil consumption thread which we already covered over hundreds of pages of detailed info of rings and egr cleaning. But no OCC mentioned in this one.
     
  4. Mendel Leisk

    Mendel Leisk Titanic Social Director

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    I think so.

    Maybe the aforementioned Oil Catch Can, on the Positive Crankcase Ventilation line between PCV valve and intake manifold, will do that.

    I did the works (including an OCC), around 70K kms, in September 2017. Checked the EGR pipe a month or two back, at 81K kms, and it was pristine. I had the throttle body off day before yesterday for a clean: there's an oil "sheen" at the low point of the intake manifold, but not a pool.

    The OCC is catching around 100~120 cc per year, and that's with only 8K kms usage.

    I don't doubt that the EGR will eventually start to clog up again, but between the OCC and periodic reclean of everything, hopefully that'll break the vicious cycle.
     
    #4 Mendel Leisk, Jun 1, 2019
    Last edited: Jun 1, 2019
  5. Merkey

    Merkey Member

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    Maybe a dumb question, but, if the catalytic converter is subjected to exhaust gas like the EGR system is, why do I not hear of more CCs getting clogged?
     
  6. gliderman

    gliderman Active Member

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    I dont know where the comparison comes from, but, the catalytic converter and the EGR cooler are two different types of animal and are not related in form or function.
     
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  7. Merkey

    Merkey Member

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    They both have contact with exhaust gas.
     
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  8. Mendel Leisk

    Mendel Leisk Titanic Social Director

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    Both the EGR cooler/valve and the Catalytic Converter:

    1. Have exhaust gas flowing through.
    2. Are subject to clogging.
    3. When clogged, cause problems.

    CC's have been in use a lot longer, they've worked out the optimum cross-section? The EGR as implemented in Gen 3 is new. For 4th gen it looks like they more-or-less doubled the cooler cross-section, and moved the EGR intake to be downstream of the Cat.
     
    #8 Mendel Leisk, Jun 1, 2019
    Last edited: Jun 1, 2019
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  9. fmerkel

    fmerkel Member

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    So, if you have a Gen3 that does not...yet....show any problems, what to do to stall/prevent this from happening?
     
  10. Raytheeagle

    Raytheeagle Senior Member

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    Drive the speed limit, go up on oil viscosity and keep an eye on the Prius chat PM’s (egr circuit cleanse and oil catch can);).

    Best thing to do is monitor the dipstick to stay ahead of it(y).
     
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  11. Merkey

    Merkey Member

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    Maybe I'm drifting too far into the weeds, but, what if post CC exhaust gas was used for the EGR system? Would it not be much cleaner? Maybe too expensive too engineer.
     
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  12. Mendel Leisk

    Mendel Leisk Titanic Social Director

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    That's what they've done, in fourth gen. I suppose you could mod a 3rd gen, but a lot of work. With 3rd gen the EGR feed pipe branches off the exhaust manifold.



    Memorable @Ragingfit quote from the above: "This came off this engine, so it better fit..."
     
    #12 Mendel Leisk, Jun 1, 2019
    Last edited: Jun 1, 2019
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  13. Rmay635703

    Rmay635703 Senior Member

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    An even dumber question but what if the egr uptake was moved posted CAT?

    Might loose a small amount of economy but the oil should be burnt off so no more gasket eroding oil chugging?

     
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  14. Merkey

    Merkey Member

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    Thanks Mendel. Good job on finding that video.
     
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  15. wheezyglider

    wheezyglider Member

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    Plus catalytic converters get over 1000F, they burn off the kind of stuff that sticks to the EGR cooler fins. And EGR valve. And EGR pipe. And Intake Manifold.
     
  16. Mendel Leisk

    Mendel Leisk Titanic Social Director

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    That's easy.

    Big kudos to @Ragingfit for taking the time and effort to document his transplant.
     
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  17. Peter123

    Peter123 Member

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    I didn't include the OCC in the writeup because it is a mod to a smog control. Notwithstanding how much good it does, it may not be legal under some governments interpretation of the laws.

    The main use of the cat cleaner is to clean the piston rings. Cleaning the cat is a side benefit.
     
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  18. Mendel Leisk

    Mendel Leisk Titanic Social Director

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    Several cars come stock with some sort of OCC, and then it's allowed.

    At least with a tightly installed, sealed-style OCC, the only reason it's not allowed is that it's not stock, service departments have no awareness of it, no published documentation, that sorta thing.
     
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  19. alanwagen

    alanwagen Member

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    There has to be a rhyme or reason that some use oil and some don't. I live in Texas where it is hot and a lot of freeway driving. I also use only Tier 1 gas and Synthetic oil. I don't use oil and never had my EGR serviced. Could it be the gas and the heat that makes a difference?
     
  20. Mendel Leisk

    Mendel Leisk Titanic Social Director

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    Have a look at the EGR pipe; it's an easy DIY. @NutzAboutBolts has a video on it, pinned in 3rd gen maintenance forum.
     
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