20 seeds per bucket? You wish!
Different things give different amount of seed oil when squeezed.
To my knowledge:
Worst: Seeds / Pumpkin seeds / Melon seeds = 10 mB seed oil per seed. (100 seeds needed per bucket)
Best: Sweet chestnut = 220 mB seed oil per nut (~4,5 nuts needed per bucket)
There should be some other nuts in between those numbers. When you need a serious amount of seed oil you want to breed some tree's to get those sweet chestnut tree's.