The ability of different types of soybean oils to plasticize micronized recycled rubber and enable incorporation into new rubber compounds was explored. Mechano-chemical de-vulcanization of micronized recycled rubber powder with the aid of different soy-derived processing oils, particularly unmodified soy oils and polystyrene-modified soy oils in the presence of tetramethylthiuram disulfide (TMTD) was investigated in an internal mixer. The effect of physical properties of oils and their chemical structures on mixing characteristics and cross-link density (CLD) of de-vulcanized rubber was studied. 1H NMR spectroscopy analysis and CLD testing confirm the ability of fatty-acid chain unsaturations in soy-derived oils to chemically interact with the rubber polymer at reactive mixing conditions. Different amount of recycled rubber powder chemically de-vulcanized in the presence of soy-based oils was used for the formulation of poly(styrene-butadiene) (SBR) rubber compounds. Vulcanized SBR rubbers were tested for mechanical properties, gel content, and CLD. Both tensile testing and CLD data demonstrate an increase of CLD in the rubbers containing reactively mixed recycled rubber, comparing to the rubber compounds containing untreated recycled rubber powder. The highest tensile strength was observed for the compounds containing polystyrene-modified soy oil used both for reactive mixing of recycled rubber and as a processing oil in SBR formulation, suggesting a positive contribution of modified soy oil on the physical properties of SBR rubber compounds.