The Hansen solubility parameters were determined for three hydrocarbon fluids, equivalent to naphthenic mineral oil of different degrees of refinement. This was done by an indirect method based on the solubility of the hydrocarbon fluids in a system of solvents with known Hansen solubility parameters. It was concluded that the method may serve is a tool to estimate the approximate solubility parameters of naphthenic oil. However, in this study, the accuracy was insufficient to separate naphthenic oil of different degrees of refinement.