I've been thinking. Some unfortunate member (typically I have forgotten who it was) recently ran a big end (crankshaft) bearing. I postulated that this was possibly due to the oilway to that journal getting blocked by the sludge trap. It occurred to me that this might make the case for using flushing oil when changing the engine oil to try to move as much sludge as possible & keep the oilways clear.
Or it might make the case for NOT using flushing oil on the basis that it might disturb stuff that is best left alone.
If it's a re-built engine I would use flushing oil from day one. But an engine that has already done a few miles? I don't know.
A near neighbour of mine had an old Ford Mondeo that she put into a local garage for servicing. The bill came to about $700 (Pounds!), which was probably close to the value of the car. When I looked at her invoice I noticed they had charged her not only for changing the oil, but for flushing oil also! Of course, in a court of law you could never prove they didn't - but what a racket!
Technical advice Q&A