In the pavement industry, the use of reclaimed asphalt pavement (RAP) material is increasing due to its cost-effectiveness. However, substituting RAP for virgin aggregates and binder can lead to poor workability and degraded overall performance of the pavement. To address these issues, rejuvenators are being employed. This study explores the effect of waste engine oil (WEO) as a rejuvenator on the volumetric properties of recycled mixtures (RMs) with different RAP contents in the direction of sustainable pavements. The study investigates the optimum dosages of WEO through Marshall stability criteria for different RAP contents. Additionally, a comprehensive cost analysis is performed to evaluate the cost of different mixtures and hot mix asphalt (HMA). Results indicate that the inclusion of RAP significantly affects the volumetric properties of bituminous mixtures, which can be restored using WEO. The optimal dosages of WEO exhibit the volumetric properties of different RMs similar to the properties of HMA or within the limits suggested by specifications. Furthermore, 12 to 29% of cost savings can be achieved associated with virgin and waste materials, their transportation, and production of bituminous mixture with using 20 to 50% RAP. This study highlights the role of WEO as a sustainable rejuvenator, enabling increased utilization of RAP.