Jens,
I have an Alfa Laval centrifuge. I will pull out water, but it will not clarify oil. The sludge you speak of is something that gravity must do, over time. One would think that 30,000G's would do the trick, but it won't. There is something much more complex going on than just simple "heavy stuff goes to the bottom". I think it is more likely that certain elements attract and form larger, heavier compounds that settle over time. Just how much heavy stuff does an engine make anyway? I don't think it is all that much.