As oil or oil additives degrade, they develop varnish and begin to accumulate this material within the oil. The amount of varnish carried by or within the oil will progressively increase as the oil continues its service. The oil’s carrying capacity for varnish will also fluctuate based on temperature. As the oil becomes saturated, this material can settle from the oil and form harmful deposits. Fortunately, varnish can be extracted from oil and measured in a laboratory by its change in color.
