<p>Asphalt binders modified with high rates of waste tire rubber frequently exhibit excessive viscosity, hindering processing and necessitating elevated production temperatures. This study investigated the performance of high contents of vegetable oils to reduce viscosity in 50/70 penetration-grade asphalt cement exhibiting excessively high viscosity, evaluating rheological and empirical responses, as well as aging effects (short- and long-term). Although vegetable oils are proposed as viscosity-reducing additives, the optimal balance between crumb rubber content, oil content, and oil origin has not yet been fully established. Binders were produced at 180&#xa0;°C by incorporating new and residual soybean and corn oils (10, 15, and 20%) into a petroleum asphalt cement containing 21% waste tire rubber. Characterization included rotational viscosity, Dynamic Shear Rheometer (DSR), Bending Beam Rheometer (BBR), softening point, flash point, and mass loss tests. Results demonstrated that the binder containing only 21% waste tire rubber showed inferior low-temperature performance. On the other hand, a 10% oil rate represents the optimal balance between workability and mechanical performance, providing an approximate 60% viscosity reduction without significant in rheological properties; above this oil content, structural characteristics are compromised. No significant differences were observed in main properties based on oil botanical origin. Complementary viscosity assessment of asphalt binders modified containing 10% residual soybean oil produced at different temperatures indicated that production at 150&#xa0;°C resulted in comparable viscosity to that obtained at 180&#xa0;°C. The use of these binders offers a viable engineering alternative for the potential reduction of processing temperatures and production-related emissions, while minimizing asphalt plant energy costs and preserving the structural durability required for road paving.</p> Graphical Abstract <p></p>