In any organization when you have plans of preventive and predictive maintenance is necessary to have tools to determine the status condition of the equipment, in the case of diesel engines are rapid tests that determine the state of the engine and lubricant, such as blotter spot test. In this paper we determine the characteristic parameters related to digital image processing of oil spots. Both instruments are developed basic procedures for taking samples of oil spot and images of these. Based on the interpretation of the oil spot given by experts and relations that estimate the dispersivity and the carbon content of the lubricant, more lab reports the sample population, we obtain a system that estimates the degradation of the lubricant.