In petrochemical industries oil-in-water dispersion separation is important due to economic, ecological, and safety reasons. If the coalescer is a part of the central unit for wastewater treatment, then it is able to separate oil with different properties in time. Designing such a coalescer is complicated even when this is based on experimental results. This work contributes to the design strategy of the coalescer for the separation of oil of different quality. In this work four different polymeric fibers were tested for separation of model dispersions encompassing four mineral oils of different properties. Experiments were carried out over a wide range of oil properties, bed permeability, and fluid velocities. Selection of filter media was made on the basis of 80 experiments. Contour diagrams which give the dependence of bed permeability, the properties of oil, and the critical fluid velocity enable reliable and easy selection of filter material for steady-state bed coalescence.