Interval based maintenance might involve which of the following actions?

Changing an oil filter every 6000 km is an action that corresponds directly to the concept of interval-based maintenance. This type of maintenance relies on a predetermined schedule or interval— in this case, every 6000 kilometers—to perform necessary tasks aimed at ensuring that equipment continues to operate efficiently and reliably. The practice is somewhat standardized in many types of machinery, particularly in automotive and machinery maintenance. By adhering to set intervals, potential issues can be prevented before they escalate into more significant problems, thereby prolonging the life of the equipment.

While the other options involve important maintenance activities, they do not specifically illustrate the concept of interval-based maintenance as clearly as scheduled oil filter changes do. Monitoring oil filter differential and verifying the operation of a pressure switch are more aligned with condition-based maintenance, which revolves around the performance and operational conditions of components rather than regular, time-based intervals. Checking for changes in sound also falls under a more observational or diagnostic approach rather than a fixed maintenance schedule.