Could you make the mod support unloading of burnt fuel? In some mods, burnt fuel is intended to be reused. If burnt fuel is lost, that makes fuel expensive in a way that the mod did not intend. Since the drone has no burnt fuel inventory, and no mooring would connect to that inventory anyway, there's no way to unload it.

Don't see why I couldn't have look
Could you give me the name or link of the mod that adds it?

Never mind, I found how it's done. I'll have a little root about

OK, so after some quick scanning I have some good and bad news

Bad news

Annoyingly, due to what moorings are in the code (proxy containers), there doesn't appear to be any way to target both the fuel and burnt fuel slots at the same time (Nuclear reactors allow you to target both at the same time, but again, this appear to not work with proxy containers)

Good news

I can think of a few workarounds
- The first and most obvious solution is to add a new mooring for burnt fuel. I'm not too fond of this since that would add even more mooring spam
- Add a different area on the mooring that specifically targets the burnt fuel slots. As an example of what I mean: the 3 tiles on the right side of the mooring allow you to access the burnt fuel slots, whereas all the other tiles would gives you access to the fuel slots
- While at the refueler, have the drone check if it has any burnt fuel, if so; have the mooring target those slots first. Once those slots are empty, switch to the fuel slots. This has a problem though, which is that anything can be put into the burnt fuel slots, so inserters pointing into the mooring would start putting fuel into the burnt fuel slots. The solution to that problem would be to have the mooring output a circuit signal based on what slots it's targeting, allow us to turn inserters on/off as needed. Making this rather complex to use, but easy to implement

Likely I'll go with the last option for now, since it's the fastest to do. But I might change it later
I would welcome other opinions and ideas though

I like the last two solutions. For two different inserter targets, there should be a rotatable mooring with visual indication of where the two areas are. The circuit method seems workable and it doesn't affect behavior at all when there's no burnt fuel, so I think it's a reasonable way to do it.

Alright, I've implemented support for burnt results. I won't release it yet as it's part of some other changes that still need more testing, if all goes well I'll have it out this weekend, but no promises

I went with the third idea for now. To enable it, you'll need to set the size of the burnt result inventory to a value higher than 0 in the settings
If enabled; Refueler moorings output a configurable signal (Default [F]) with a value of 1 if the fuel slots are targeted by the mooring, and a value of 2 for the burnt result slots. I'll also add it to the cheat sheet when I release the update

Note that Cargo Drones does not check how full those slots are when deciding when to go to a refueler, it makes that decision completely based on the fuel slots

That's good to hear. Thank you for adding this feature.

Released. Update to 1.4.0 and remember to set the inventory size in the options
If you want changes, don't hesitate to comment