I see no issue with carrying lots of oil. I sometimes keep a 5qt jug on hand, since I don't buy 1qt containers ever.

I still think tape over the hole would have sufficed. At least on the M54, there isn't much crankcase pressure (even a slight vacuum at idle) so just multiple strips over the hole would be ok. The motor shouldn't be blowing it off, and then you'd have a cover to stop the oil from splashing everywhere.

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