I have 2014 Prado 150 series D4D. I am trying to get an understanding of how fuel is managed to, from and between the fitted dual fuel tanks, main and secondary. I'm aware that fuel is transferred (pumped) from main to engine and return (for cooling purposes) at 60.0L/hour. How fuel is distributed and sequenced between tanks is the mystery for me. My questions therefore are (1) When refueling, does main fill first then overflow to secondary, or do they fill simultaneously and equally? (2) During consumption, in what sequence do the tanks drain e.g. (a) simultaneously and equally (b) main first followed by transfer, secondary to main (c) main, to a certain residual volume then transfer, secondary to main (d) other? Also, how is fuel transferred between secondary and main, pumped, siphoned or drained? And further, what is the role of the so called "transfer pump", inter-tank fuel transfer or transfer between tank and engine, or both? When considering the possibility of water contamination, these would seem important questions to understand? Cheers.