Predictive test method for coking and fouling tendency of used lubricating oil

A short, reliable test has been developed to measure the coking and fouling tendency of used lubricating oils undergoing thermal stress. The technique utilizes commercially available instrumentation and requires only 200 mL of sample and three hours analysis time. Correlations based on oils of known quality demonstrate good qualitative predictive abilities, while reproducibility studies demonstrated quantitative reliability. It is shown that ash content alone may not always be a reliable measure of fouling potential.