“…An important characteristic of a lubricant is the ''Remaining Useful Life'', which represents the remaining time, in which the lubricant becomes unfit for the operation in continuous use. However, the lubricant degradation pattern also depends on the characteristics of the machine, in which the lubricant is applied, see [32] and the references therein. For robotic applications, preventive, scheduled maintenance can be performed to verify the quality of the lubricant in actuators and transmissions [5].…”