The IMPA-ModFD-2 model of the feedstock mixture for mathematical modeling of selective treatment of deasphalted product was developed and combined with laboratory modeling on real mixtures and allows using the advantages of both methods for developing new and improving existing processes and equipment. A general description of the mixture and its structural-group composition are presented. A special feature of the mixture is the presence of sulfur-containing components. This allows calculating one of the key indexes in treatment of deasphalted product - the sulfur content, which is significantly limited in selective treatment raffinates. The results of the mathematical modeling shows the acceptable agreement with the analytical data.