Automotive dampers are essential vehicle components regarding vehicle dynamics by keeping the road contact and reducing wheel load fluctuations. So damper degradation could not only significantly influence driving comfort but also the dynamics and therefore driving safety. The aim of this study is to expand knowledge about the behavior of passive automotive twin-tube dampers degraded by loss of oil and pressure. This serves to improve the understanding of inner processes of the damper and modeling the behavior of degraded dampers. To analyze the damper behavior, an intact damper has been modified and validated to allow adjusting the oil and pressure level. Using a dynamic hydraulic damper test rig a preconditioning routine for degraded dampers is developed. With this routine, a wide measurement program at various amplitudes, frequencies, oscillations, and damper configurations is carried out and the obtained results are discussed. The conducted measurement program did not cover small amplitudes (<8.4 mm) and high frequencies (>19 Hz). The results show that the loss of oil or pressure leads to complex dependencies on all varied parameters such as amplitude, frequency, number of oscillations, and waiting time between two measurements. While the absence of pressure only leads to small performance reductions, especially the loss of oil leads to significant deterioration of the damper performance. Already at a level of 90% of the original oil volume, the examined damper loses up to 30% of its performance under disadvantageous operating conditions. Furthermore, the loss of oil can make a damper almost useless when 40% of the oil is still present.