The modeling of the viscosity of thermoplastic materials for injection molding simulation including the dependence of viscosity on shear rate, temperature and pressure is well established. However, little attention has been given to the influence of fiber orientation on viscosity. In this work, a framework is presented for viscosity model research which allows the easy implementation within the flow simulation of various proposed models which depend on the evolving prediction of fiber orientation at each time-step. Potential orientation dependent models are evaluated and their influence on the fill pattern and filling pressure are compared with actual molding data. In addition, the coupling of fiber orientation and viscosity is found to influence the through-thickness profile of fiber orientation itself due to the modification of the velocity profile distribution. This demonstrates that the effect of orientation on viscosity has a role to play in improving the modeling of fiber orientation.