I'd degrease it and check it in a weeks time. Start with a clean surface, go from there. If the o ring is installed correctly and the housing and cap are not damaged, then no oil leakage should occur.

A common mistake for young players is to clean the cap and the housing till they are basically spotless, then install the new filter and o ring. A dry surface does not allow an o ring to seal properly, as it binds on the surfaces when the cap is installed. Needs a coating of oil.

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Cheers,

Anthony