Computational Fluid Dynamics has emerged as a powerful tool to analyze and optimize fluid systems. This enables engineers to design and optimize, relying less on physical experiments, hence reducing the time and monetary efforts required in product development. The gearbox (a.k.a. transmission) is a necessary mechanical system, predominantly in industrial and transportation applications. High speed and high torque applications require good lubrication to reduce power loss and avoid component failures due to overheating, wear, fatigue, pitting and scuffing of gears. These damages are expensive to repair. The lubricant forms a film between the moving components, dissipating generated heat and reducing friction and wear. With the help of CFD, engineers can simulate lubrication within the gearbox and predict key parameters such as pressure, velocity and temperature distributions. Potential issues like overheating of surfaces, insufficient lubricant levels can also be identified, and lubrication flow rates can be optimized to increase the life of the drivetrain. It is also possible to compare the performance of different lubrication systems and lubricants. This presentation provides an overview of gearbox lubrication using a powerful Lattice-Boltzmann based CFD solver – XFlow. Churning loss in a dip lubricated FZG gear test rig of type C-PT, at different speeds and temperature is analyzed and compared with experimental results.