One of the main advantages of Fluidic oscillators is that they do not have moving parts, which brings high reliability whenever being used in real applications. Nevertheless, before thinking of using these devices in the real world,it is necessary to evaluate their performance, since each application requires a particular injected fluid momentum and frequency. In this paper, the performance of a given fluidic actuator is evaluated via a full 3D-CFD analysis, flow is considered as compressible. The evaluation is based on studying the output frequency and amplitude whenever the feedback channels length/width are modified. Initially a standard fluidic oscillator at several high Mach numbers will be simulated. In a second step, several feedback channels length/widths will be considered.