I never really thought about oil's ability, or inability, to keep additives in suspension, but it certainly makes sense that if oil sits without agitation for a prolonged period of time, heavy additives will settle. Is that really a consideration in a wet sump configuration? I ask because the oil pick-up is very close to the bottom of the oil pan, and it seems to me that whatever liquids are down there are going to be picked and pumped through a running engine, quickly producing a homogeneous liquid.
I know nothing of dry sump applications, so it seems to me that oil additive separation is a greater concern in a dry sump.
I find discussions like this to be very informative and interesting.
Steve