Methane-ethane and methanol-ethane binary mixtures were simulated by the Gibbs ensemble Monte Carlo method. Thermodynamic properties and structural characteristics of coexisting fluid phases were calculated. Reasonable agreement with experiment was obtained, in particular, for the liquid-liquid-vapour coexisting pressure in the methanol-ethane system at 298.15 K. A lyophobic effect, which affects the phase behaviour and the hydrogen-bonding characteristics of the liquid phase, was observed. in order to improve agreement with experiment, the values of the Lennard-Jones interactions parameters for CH3OH and C2H6 molecules were adjusted.