We improved mixing of high viscosity fluids in a stirred reactor used in a petrochemical process, balancing blend time, shear exposure and energy use. A computational fluid dynamics model with appropriate rheology was developed to study stirred vessel mixing under realistic operating envelopes, varying impeller type and diameter, clearance, baffles and shaft speed. Where available, electrical resistivity tomography and drawdown observations were used qualitatively to validate flow structures and stratification trends. Key performance indicators included blend time proxies, dead zone volume fraction, power number and wall shear statistics. Specific impeller and baffle combinations eliminated persistent low shear pockets, reduced blend time and improved suspension without excessive power penalty. Mesh and turbulence model sensitivities confirmed the robustness of option to option comparisons. The recommended configuration delivers more uniform product quality with lower energy per batch, and the calibrated model now supports ongoing scale up and what if studies for Ingevity’s operations.