Is discolouration of oil a warning sign?
Discolouration is natural for engine oil when it is used; in fact, discolouration is a sign that the oil is doing its job. Engine oils contain dispersants which are designed to hold contaminants, such as combustion by-products, in suspension within the oil. These contaminants provide a dark colour to oil. Therefore, simply by doing its job, an engine oil will turn dark with use. The extent of oil deterioration is determined through the use of a wide range of physical and chemical tests, but colour is not one of them. The GM Engine Oil Life System is designed to account for oil deterioration and a darkening of the oil with use is expected and natural.
