Description of the issue:

mekanism's tank is not being treated as a returned empty bucket on making treated wood with Creosote Oil, I'll relay this info on Mekanism's git if someone thinks this is on mekanism's end

Versions & Modlist

IE: 1.16.3-4.1.1-127
Forge: 34.1.42
Mekanism: 1.16.4-10.0.17.444

As far as I can tell, Mekanism's tank items do not implement getContainerItem.

https://github.com/mekanism/Mekanism/blob/1.16.x/src/main/java/mekanism/common/item/block/machine/ItemBlockFluidTank.java

They should totally do that, and reduce their stored fluid by BUCKET_VOLUME. Report to Mekanism please.

This issue was closed without a solution on the Mekanism issue tracker, could you perhaps have another look?
Or perhaps block the Tank from Mekanism from being used at all for your fluid recipes? Having high tier tanks full of creosote voided isn't a great user experience :)

Yeah, I'm aware that Mekanism has declared this not their problem. We'll fix this at some point, probably. Just use a bucket for now.

Thank you! :)