Diesel fuels enhanced with nanoparticles like \(TiO_{2}\) and \(CuO\) offer improved engine performance and fuel efficiency, but contribute to entropy generation and environmental pollution, including harmful emissions and byproducts. To address these challenges, micropolar fluids are utilized with nanoparticle-based diesel fuels to enhance oil/water separation processes, reduce impurities, and mitigate pollutant formation. This study conducts a comparative numerical investigation of entropy generation in the unsteady, unidirectional flow of two systems: (1) an immiscible \(TiO_{2}\) -Diesel B0 nanofluid with a micropolar dusty fluid and (2) an immiscible \(CuO\) -Diesel B0 nanofluid with a micropolar dusty fluid. The objective is to evaluate the thermodynamic irreversibility associated with each nanoparticle type under realistic operating conditions. The flow is driven by a time-dependent external pressure gradient, with a transverse magnetic field applied. The modified Cubic B-spline differential quadrature method is employed to solve the system's coupled partial differential equations. Key flow parameters as the Reynolds number, radiation parameter, micropolar parameter, and nanoparticle concentration, are analyzed for their effects on entropy generation. Results show that \(TiO_{2}\) generates higher entropy across most parameter variations, primarily due to its higher thermal conductivity and stronger response to flow and temperature gradients. In contrast, \(CuO\) consistently produces lower entropy, making it a more effective option for reducing energy losses and thermodynamic irreversibility. These outcomes highlight \(CuO's\) potential for improving system efficiency and supporting the development of strategies aimed at minimizing pollutant formation and achieving cleaner, more sustainable combustion processes.
