In the course of my current game, I've lost on the order of tens of thousands of petroleum gas from moving requesters, rebuilding, upgrading etc. It would be a minor nice-to-have if the fuel trucks would remove fuel from requesters if there aren't any drones in it. In this way, I could remove the drones, let the last of the resources be used (or remove them myself) while the fuel drones take fuel back to the fuel depot.
