It is not the intention of this chapter to attempt to turn the Master into a Chief Engineer. It is merely meant to familiarize the seagoing Master with some basic elements of the activities and developments in the subject of marine engineering. Most serving Masters would have at some time in the past experienced the request from the engine room to reduce speed because of a ‘scavange fire’, but the question should then arise, what caused that fire? The fact that the most common cause is worn piston rings begs the question, why is the vessel operating with worn piston rings in the first place and is the function of planned maintenance fulfilling the vessel’s needs?