The fate and transport of oil spilled in soil has long been a focus for experimental and theoretical research in subsurface hydrology. Oil transport in the soil is affected by a large number of physical, chemical and microbial processes; and the properties of the media. This study is a two layer problem containing horizontal oil layer overlying the subsurface topsoil region saturated with oil and water (native fluid). To explain the method by which the convective flow in the oil region affect the transportation of oil, modeling is carried out in two regions (oil and topsoil). The two dimensional, transient oil flow equations for both the regions include thermal and concentration buoyancy effects. The species equations include the effects of energy flux caused by the temperature gradient on the unsteady advective-diffusion equation. The resulting fluid flow, heat and mass transfer processes are discussed numerically with the aid of graphs. The validity of the results obtained is verified by comparison with available results and good agreement is found
