Oil can be used in mob farms to push items without mobs swimming around

[loud knot]

While designing my early game witch farm I needed a solution to move items off the spike that was killing the witches.
While water does work, the mobs try to swim up in it and it reduces the farm's efficiency.
And then I thought of Oil - it doesn't allow entities to swim up in it, and it still pushes the entities inside of it (slowly, but you can just switch to a different transportation method after getting the items out of the killing chamber)

[viscid prairie]

Soycake uses Spectre Glass from random things to achieve the same thing, Mobs don't interact with the block, but items inside spectre glass bounce around randomly until they are off of the spike