RCM vs. PM optimization: when to use which
RCM and PM optimization (PMO) are often treated as rivals. They start in different places, and they can be used on the same plant without contradiction if you are honest about the starting point.
RCM, as framed by the seven questions in SAE JA1011, starts from functions and works down to tasks. It is the better tool when the system is critical, the current PMs are not trusted, or you do not actually know which failures you are trying to manage. It takes more facilitation time. It produces a task list that can be compared with the one you have, rather than a tidy edit of that list.
PMO starts from the existing preventive maintenance program. You ask, task by task, whether it still addresses a failure mode, whether the interval has evidence behind it, and whether a mode has no task at all. It is faster when the program is already documented and the goal is to cut low-value hours and close obvious gaps. It will not invent a function you never wrote down.
A practical pattern in a plant without a reliability department is to PMO the bulk of the program and reserve RCM for a short list of critical systems. See PM audit and optimization and RCM facilitation, and the PM Program Audit Toolkit.