Vegetable Oil is a generic term for Oil made from vegetable sources, and the name given to oils which have been mixed together. Mixing seed types in the Press will produce a non-specific "Vegetable Oil", as will mixing Oils in a Barrel or Bucket, or Oiling Trough.
If you need a specific kind of oil like Corn Oil), be careful not to accidentally mix it with other kinds.
There are currently 4 kinds of Oil in the game:
- Vegetable Oil (mixed oils)
- Corn Oil: 100 seeds = 5L
- Cottonseed Oil: 100 seeds = 10L
- Pumpkinseed Oil: 100 seeds = 7.5L
Using less than a full stack of seeds will simply result in that fraction of oil being produced. 20 Seeds of Corn will give you 1 Liter of Corn Oil when pressed, and 80 Seeds of Pumpkin will give you 6 Liters of Pumpkinseed Oil.