THE authors suggest that four factors are involved in the formation of low-temperature engine deposits: fuel, lubricating oil, operating variables, and mechanical conditions.
They present the results of a laboratory investigation to determine the effect of these factors, including fuel composition, lubricating oil characteristics, jacket temperature, crankcase oil temperature, intake mixture temperature, air-fuel ratio, oil change frequency, oil filters, and crankcase ventilation. They make recommendations for minimizing the formation of the deposits in service.
Several field service tests to determine the effectiveness of some of the variables are described. They report that the results of these tests substantiate the laboratory findings and indicate that engines can be kept clean for long periods by selecting the proper combination of corrective measures.