The above fills the boiler with 24 spoilage: However as you can see, the "automated insertion limit" according to the tooltip is 5.
Now I've tested spoilage with every entity I could find in the lua prototypes that takes burnable fuel.
When there fuel slot is empty, regardless of what fuel is in it, they all seem to display 5 as the automated insertion limit.
However, after testing, for spoilage it is usually not 5:
- For burner Inserters (1 slot), Cars (1 slot), Tanks (2 slots), Heating Tower (2 slots), Locomotives (3 slots): 200 for each slot (i.e. the stack size of spoilage)
- Boiler: 24
- Burner Generator: 12
- Burner Mining Drill, Stone Furnace, & Steel Furnace: 5
(For nuclear fuel though, the limit is always 1, which is the only time it's less than 5).