Displacement x RPMmax /2 = CFPM (make sure you get the CC/Cubic Inches right) then calculate the fuel needed for that air flow rate to obtain the fuel flow rate at the air/fuel mixture ratio. Or figure the rate you could burn fuel at at max speed with maybe 45mpg at 90mph = 2 gph then convert the units to cc/minute.
So are you going to shift to the GM Sychromesh fluid? I can somewhat relate to the question about using gear oil in the Swift. If Honda has me putting in engine oil, I would think the Swift would definitely need a similar viscosity.