Lubrication is a crucial element in the efficiency and life-expectancy of any piece of equipment with moving parts. Lubricants have many functions, but their main purpose is to form a protective barrier between the metal surfaces of critical machine components. Overtime, the lubricant in the machine breaks down to where it can no longer protect the machine. At this point, the lubricant must be changed, and the machine must be filled with a fresh batch of lubricant. This period of time is often referred to as the drain interval.