The lab I use is Polaris. The really nice thing about analysis is being able to track trends over time, and Polaris provides the graphs. If you really want to flush your system, you should use a dedicated flushing agent for the job. You run it for 2-3 days prior to changing your oil. By the way, if you were judging your soot loading by how black the oil was, it's not really useful to do that. Soot is something for the lab to look at, along with fuel dilution, TBN and a whole host of other things. If you want the whole story, PM me.that's great feedback... wow.. 45k miles ... great suggestion about using a lab.
which lab do you use?