In this study the mechanical shear degradation of lithium-thickened grease was evaluated using an in-house-developed aging rig and a commercial rheometer. It was found that this grease loses its original consistency during aging and shows a two-phase aging behavior. In the first phase, primarily reorientation and breakage of the thickener network take place, resulting in a progressive drop in the grease's rheological properties. After this, the aging is dominated by the breakage of smaller fiber fragments and the grease degrades at a much slower rate.