Ground tire rubber (GTR) from whole passenger car tires is devulcanized using the conditions which are the best compromise for tire rubbers. The elaboration of the optimal devulcanization process for GTR is performed in order to obtain a homogeneous and high degree of devulcanization. Swelling of GTR in a mixture of an oil and a devulcanization aid before devulcanization was studied as a way to achieve a more homogenous breakdown of the crosslink network. Further optimization of the parameters in terms of devulcanization oil loading and process time were elaborated. By using these optimized devulcanization conditions, a significant reduction of crosslink density can be achieved for GTR.