PSMO test

The rate of formation of deposits was measured using the Penn State thin-film microoxidation (PSMO) test. The volatility and deposit-forming tendency of the three oils were determined. The conditions at which the tests were conducted in this study are shown in table 21.1. The deposit-formation induction time in the PSMO test was used as an indicator of the deposit-forming tendencies of the oil. The test method was developed to evaluate automotive engine oils [7] and later expanded to study other lubricants [8]. The test procedures are desaibed in detail in the literature [9]. 

The PSMO test was utilized to study the used-oil volatility and deposit-forming tendencies. The volatility loss for the new oils at 225 C is shown in fig. 21.5. The volatile losses of the oils plateau at about 80%. This is partly due to the formation of deposits, which results in a reduction in the availability of liquid product. 

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