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The hardness of various types of soot produced by heavy- and light-duty diesel engines of European, Japanese, and North American designs was measured by low-loss electron energy-loss spectroscopy (EELS). No clear general trend can be established that shows heavy-duty diesel engine soot is necessarily harder than light-duty diesel engine soot. The variation in hardness among individual soot particles produced by the same diesel engine can be as large as differences between the hardest soot particles produced by heavy-duty diesel engines and the softest soot particles produced by light-duty diesel engines. There are heavy-duty diesel engines that can produce soot that is softer than that produced by some light-duty diesel engines and vice versa. Nevertheless, the hardness of all types of soot studied is close to the range of hardness of metal engine parts. Thus, the results indicate that soot is hard enough to abrade some metal engine parts.

In automatic transmission technology development the degradation of paper friction plates has often been considered a major failure mechanism by which transmissions lose their anti-shudder characteristics. One of the most common degradation processes for paper friction plates is known as glazing. In this study, we focus on the relationship between friction plate glazing and anti-shudder durability in the Japanese Automobile Standards Organization (JASO) low velocity friction apparatus (LVFA) rig test following the procedure M349-98. We also investigate the impact of used friction plates and used oil on torque capacity durability as measured by an SAE No. 2 machine following the JASO procedure M348-95. We find that friction plate glazing has no correlation with anti-shudder durability. A completely glazed plate can have long anti-shudder durability but a barely glazed plate can have short anti-shudder durability. The basic reason for the lack of correlation is that friction plate glazing does not affect boundary friction coefficients. In almost all the cases studied, changes in fluid properties have a greater influence on boundary friction than does surface glazing.