[skygazer]

I’m sure I’m being daft, but how would that arrangement function as a self cleaning filter?

[josh_frome]

The sisal rope will wick based on the elevation change and deposit clean oil to the lower receptacle.

[skygazer]

Ah, so the sisal rope is just a simple filter, and not a "continuously self-cleaning" filter? I presume it's eventually fouled and must be disgarded? So this must not have been to which the ancestor was originally referring.