One promising bacterial strain (B3), recovered from petroleum-contaminated soil. The isolate was able to produce biosurfactant. Alkyl acrylate–vinyl acetate copolymer was prepared using varying lengths of the alkyl chain. In this study, the effect of copolymer additives along with biosurfactant on the crude oil wax crystallization method has been examined by solid point test and viscosity index measurement for gas oil. The FTIR spectrum analysis of the biosurfactant showed that it was a polymeric molecule. The application of only copolymer having a side- length of the chain of C13 and C22 reduced the solid point of gas oil by 3 and 9 oC respectively. Furthermore, the same copolymer along with biosurfactant decreased the solid point of gas oil by 15 and 21 oC, respectively. Many copolymer additives blended with biosurfactants, it is assumed that it might be used to slow the formation of wax crystals and shape shorter crystals. Because of this shift in crystal form, wax crystals' capacity to intergrow and interlock is substantially reduced. By increasing the length of the alkyl chain and mixing the copolymer and biosurfactant, the viscosity index of gas oil was raised. The blend P3 and P4 additives were also proved to a better viscosity index modifier at all concentrations in gas oil.