i'm playing around with train refueling and schedule interrupts. I just noticed that it seems not to work as expected when using mixed fuels or upgrading fuels.
Lets say we start a train with 3 stacks of wood (fuel slots A/B/C) and the refuel interrupt condition is "All Locomotives (Fuel Parameter) < 50"
To my observation a train burns its fuel always from the most-left fuel slot.
After some time the fuel will look like this:
Slot A = <empty>
Slot B = <empty>
Slot C = Wood (49)
Then the interrupt kicks in and the train goes refueling. Lets say we refuel now with coal.
The train will leave fuel station like this:
Slot A = Coal (50)
Slot B = Coal (50)
Slot C = Wood (49)
First Problem occurs: The refuel interrupt condition is still true, as the "Fuel Parameter" seems to check every fuel slot separately and not total fuel per locomotive. I can understand why, because the wildcard should exchange itself with 1 symbol of matched fuel. But unfortunately we cant use the other signals like Everything / Anything / Each.
But ok, lets change our refuel interrupt condition to fix that to: "Wood < 50 AND Coal < 20". Its working, but already feels very bad.
After some time fuel will look like this:
Slot A = <empty>
Slot B = Coal (19)
Slot C = Wood (49)
Interrupt condition will be true again and train goes refueling.
But this time with solid fuel:
Slot A = Solid Fuel (50)
Slot B = Coal (19)
Slot C = Wood (49)
....
And our interrupt condition will be again always true, so fixing it again: "Wood < 50 AND Coal < 20 AND Solid Fuel < 10".....

As you see that can't be the solution. Coal and Wood will also never be burnt by the train as it refuels before (beginning at the most-left slot).
So I would expect 2 changes: Burning fuel starts on the most-right fuel slot, while refueling on the most-left slot and please let us use signals like Everything / Anything / Each on Fuel Conditions.
How did you solve that "mixed fuel" problem?
P.S.: Unloading old fuel everytime manually is not a suitable workaround
