Bob, FSS is what you say it is, with one difference. The sensor in the oil pan measures temperature, level, and di-electric ability. This is used to calculate the amount of impurities in the oil. The other factors you mention are also used in calculating service intervals.When I attended technical training in'97 we were told that piston ring "blow-by" was the major factor in oil contamination. With the development of the "modular" 112/113 engines the engineers were confident that the "blow-by" problem would be enormously reduced, and they were right. In previous years the oil was contaminated well before it lost it's other attributes. FSS was developed to take full advantage of the new piston ring/cylinder wall design, allowing the oil to effectively do it's job for a longer period of time. I'm certain the logic behind this was to keep the maintenance costs down.