The pressure drop of glass-fiber and cellulose filter media when loaded with oil-coated particles was investigated. The focus of this study is to develop a model describing the pressure drop of fibrous filter media under the above particle loading condition. A set of experimental data collected in the previous work was used for this modelling. For the cases loaded with particles having the oil volume percentage less than 50%, a loaded filter was divided into two layers: one layer for collecting all test particles (its layer pressure drop is estimated using the modified Bergman’s model) and the other layer remaining clean (its layer pressure drop is calculated using the equation of Davis). The total filter pressure drop is the summation of layer pressure drops. For the cases loaded with particles having oil volume percentage greater than 50%, the experimental data was fitted by a power equation with two parameters (i.e., the exponent, n, and critical volume, Vcr). The correlations of the above parameters with the solid-core diameter fraction (X), and the viscosity of coating oils were obtained for glass-fiber and cellulose filter media.