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Thread: Can use of mineral oil cause a newly built engine to leak?

  1. 06-16-2024, 09:45 AM #1
    Einar Irgens
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    Can use of mineral oil cause a newly built engine to leak?

    There is oil spill underneath/behind the pulley that is mounted at the end of the crankshaft. Is it possible that the rubber has deteriorated because I use mineral oil? The engine was totally rebuilt two years ago.

    https://www.design911.com/p/front-ma...--996t---997t/

    Einar
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  2. 06-16-2024, 10:03 AM #2
    72targa
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    Has it been run in the two years since it was rebuilt? For reference, what engine oil and viscosity grade is in this rebuilt engine?
    Peter Kane

    '72 911S Targa
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  3. 06-16-2024, 11:38 AM #3
    Einar Irgens
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    Very little. I have driven about 2500 km with it. Not sure about the grade, I think 20W-50 or 10W-30.
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  4. 06-16-2024, 06:06 PM #4
    HughH
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    the advice I have always been given is that mineral oil is much less likely to leak than synthetic oil which is why i never use synthetic oil in my car
    Hugh Hodges
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  5. 06-16-2024, 07:44 PM #5
    Scott A
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    One thing that makes a seal leak is corrosion on the crankshaft.
    The corrosion is rust dots that acts like sand paper and kills the seal. It tears it up.


    That’s just one cause of a seal killer, that is not related to chemicals.

    Current long term ownership: 63 Cab, 71 911, 74 914
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  6. 06-20-2024, 02:21 PM #6
    66S
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    The leak could be from the #8 main bearing o-ring on the outer surface. Tough one to fix.
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  7. 06-20-2024, 09:45 PM #7
    Einar Irgens
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    Could you tell me more, please? Is this the o-ring in the link?
    Einar
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