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Reliability analysis of engine oil using “polygraph approach”

B. Sharma (G.B. Pant Engineering College, Pauri, India)
O.P. Gandhi (Indian Institute of Technology, Industrial Tribology, Machine Dynamics and Maintenance Engineering Centre, New Delhi, India)

Industrial Lubrication and Tribology

ISSN: 0036-8792

Article publication date: 20 June 2008




The lubricating oil is a non‐renewable source of energy and its useful life is limited due to deterioration during its usage. It is desirable to maximize its use to conserve this scarce resource. At present, continuation or change of the engine oil is decided, based on the manufacturer's recommendation and experience. The suggested engine oil change period is conservative and results in non‐efficient usage of engine oil. This practice needs refinement to include all possible properties/attributes of engine oil and use of appropriate procedure to assess its realistic performance. The paper aims to analyze the procedure.


Oil reliability polygraph is used to analyze the engine oil performance during operation. Reliability analysis of the engine oil is carried out by comparing the area of oil reliability polygraph at a given operation time with the area for the fresh engine oil. The suggested procedure is illustrated by means of an example.


Physical and chemical properties responsible for performance degradation of the engine oil are considered as engine oil reliability attributes. The value of these attributes from time to time, obtained by analyzing samples drawn from the system, is analyzed through oil reliability polygraph. In this approach, the engine oil reliability attributes at a given operation time are represented in terms of reliability value to obtain the “oil reliability polygraph”.


The suggested procedure will be helpful for maintenance personnel in taking planned maintenance action.



Sharma, B. and Gandhi, O.P. (2008), "Reliability analysis of engine oil using “polygraph approach”", Industrial Lubrication and Tribology, Vol. 60 No. 4, pp. 201-207.



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Copyright © 2008, Emerald Group Publishing Limited

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