Viscosity of Motor Oil Degradation

In this application note, viscosity profiles as a function of shear rate at room temperature are presented for new and used samples of 0W-20 engine oil.  The results demonstrate how viscosity measurements can be used to determine the quality of motor oil after use.  Although this study focuses specifically on automotive motor oil, the results are applicable to other types of industrial oils and lubricants as well.

Motor oil is used to reduce the friction and wear on moving parts in internal combustion engines.  The performance of a given motor oil is heavily influenced by its viscosity.  Because of this, oils are graded by the Society of Automotive Engineers (SAE) according to their viscosity profiles.  In this study, 0W-20 oil is measured.  The ‘0W’ refers to the SAE viscosity grade of the oil at cold temperatures, and ‘20’ refers to its viscosity grade at hotter temperatures. 

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