Factorio train station, one refinery, three fluid wagons
I'm working on a challenge with only trains and necessary pumps for logistics. No belts, no bots, no pipes, no chests, no chained inserters, no unnecessary pumps. One of the trickiest parts was getting all three fluids out of the oil refinery.
The train alternates picking up 2 and 1 fluids, then when the most common one is full it proceeds to the unload station. The rear pickup station and the unload station have the same name, pathing is controlled by closing the signals on each side of the train based on the fluid quantity at the front pickup station.
Blueprint in comments.