Alternative Solution #4

 

     This solution, I believe, will be one of the simplest solutions to construct. In this design the oil-like substance will easily flow through holes (size yet to be determined) that will be located toward the bottom of the two interior walls of each tank. The oil will flow into each of the tanks almost at the same time and will fill the tanks a lot faster than in the third solution. Since the oil-like substance will only fill each tank 3/4 of the way, the chances of the liquid to spill if the tanker moves is less. This solution would also be made out of water-proofed wood and hot glue or caulk.