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Thread: Flathead Engine Oil?

  1. #1

    Flathead Engine Oil?

    Please can someone advise what oil is recommended for a 8RT/8BA Flathead? I have a copy of the original shop manual but the oils referred to pre-date modern multi grades.
    Also, is it OK to use synthetic oil? I have heard that these are not compatible with old engines and attack the gaskets and seals?
    Grateful for any advice and assistance.

    Sent from my SM-G950F using NSRA mobile app
    Rome wasn't burned in a night

  2. #2

    flathead engine oil

    Quote Originally Posted by Graham Thompson View Post
    Please can someone advise what oil is recommended for a 8RT/8BA Flathead? I have a copy of the original shop manual but the oils referred to pre-date modern multi grades.
    Also, is it OK to use synthetic oil? I have heard that these are not compatible with old engines and attack the gaskets and seals?
    Grateful for any advice and assistance.

    Sent from my SM-G950F using NSRA mobile app
    Morris 20w50 works fine as will most 10w40 20w50 high zddp oil(around 1200ppm) don't use synthetic. Also if you are not running a full flow filter change it regularly.
    Last edited by 66elcamino; 22-07-19 at 02:22 PM.

  3. #3
    Thanks for the response and advice. Is high zddp high zinc? I aim to change about every 1000 miles.
    Quote Originally Posted by 66elcamino View Post
    Morris 20w50 works fine as will most 10w40 20w50 high zddp oil(around 1200ppm) don't use synthetic. Also if you are not running a full flow filter change it regularly.
    Sent from my SM-G950F using NSRA mobile app
    Rome wasn't burned in a night

  4. #4
    No need to reply, an internet search has confirmed what high zddp is. Thanks again
    Quote Originally Posted by Graham Thompson View Post
    Thanks for the response and advice. Is high zddp high zinc? I aim to change about every 1000 miles.

    Sent from my SM-G950F using NSRA mobile app
    Sent from my SM-G950F using NSRA mobile app
    Rome wasn't burned in a night

  5. #5
    you dont need an oil with high zinc levels in a flathead, the valve springs dont have a lot of pressure on them so its not hard on the cam. i use straight 30w and change every 1500 miles with a filter. If the engine is old and has deposits/is dirty inside i wouldnt use a modern oil as it will loosen the deposits sending them all through your engine and possibly cause harm.

    Your emotions will always interfere with your sense of truth

  6. #6
    Thanks for the advice. Appreciated.
    Quote Originally Posted by weemark View Post
    you dont need an oil with high zinc levels in a flathead, the valve springs dont have a lot of pressure on them so its not hard on the cam. i use straight 30w and change every 1500 miles with a filter. If the engine is old and has deposits/is dirty inside i wouldnt use a modern oil as it will loosen the deposits sending them all through your engine and possibly cause harm.
    Sent from my SM-G950F using NSRA mobile app
    Rome wasn't burned in a night

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