An interacting lattice gas model is used to study flow of immiscible components A and B (molecular weights MA and MB,MA<MB) by Monte Carlo simulations. Concentration gradients and hydrostatic pressure bias (H) drive these constituents from their source at the bottom against gravitational sedimentation in an effective medium. Response of their flux densities (jA,jB) to the hydrostatic bias H are examined. If both constituents are released with equal probabilities (a non-interacting source), their flux densities respond linearly to bias with jA>jB except at the extreme bias H→1 where jA→jB. Flow response becomes complex if the constituents from their source are released according to their current lattice...</mb)>