There are two ways to take a Scheduled Oil Sample (S.O.S.) - by using an oil valve probe or by vacuum extraction when the engine is at normal operating temperature. After it’s taken, the sample is placed in a carefully labeled bottle and sent to the dealer’s S.O.S. lab. There it is checked for water, glycol, fuel and trace elements, such as sodium, silicon, chromium, aluminum and iron. If the sample indicates potentially troublesome elements or fluids, your dealer will contact you to discuss corrective measures. Take oil samples regularly, so that a change in magnitude of one or more of the elements can be observed, the correct diagnosis made and remedial measures taken. The goal is to identify potential problems early and avoid major engine failures.