Lightweight metals such as Al and Mg alloys have been increasingly used for both structural and non-structural applications in transportation industries for reducing mass. Joining these lightweight materials using traditional fusion welding is a critical challenge for achieving optimum part performance, due to degradation of the constituent materials properties. Friction stir welding (FSW), a solid-state joining technique, has emerged as a promising technique by demonstrating great versatility to adopt these lightweight materials. High joining efficiency has been achieved for FSW of various Al alloys and Mg alloys separately. Recent work on FSW of various dissimilar lightweight materials also show promising results based on quasi-static shear performance. To bring friction stir welding of dissimilar alloys to automotive applications, satisfactory performance under complex loading is essential. In this study, a rolled Al alloy AA6022 and a high pressure die cast Mg alloy AM60 were friction stir linear welded in a lap configuration under various welding speeds. Both lap-shear and coach-peel performances of the dissimilar welds were evaluated under both quasi-static and cyclic loading, using 30-mm wide specimens. Results indicated high lap-shear strength, but much lower coach-peel strength for both quasi-static and fatigue tests. The ratio of coach-peel to lap-shear failure load can be as low as 0.1 and as high as 0.3. The dramatic differences in weld performance under different loading configurations are explored through metallurgical and fractography analysis.