Exactly! That was the whole idea. Back when FSS was first introduced, MB told us that fuel contamination from normal "blow-by" was the major cause of oil breakdown. The oil sensor has the ability to measure to measure the amount of contamination, and determine when the oil can no longer do it's job. That's where the flexible part of "Flexible Service System" comes in. Different driving conditions such as operating temperature, engine load, etc, along with variations in engine tolerances and fuel quality are all contributing factors. The way MB sees it, why change the oil if it's still capable of providing adequate protection?