The newer HD diesel oils, especially the CF-4 and higher oils, are specially formulated to deal with "top grove fill."
Top grove fill is when oil breaks down and leaves deposits behind in the ring land. The top ring especially will at first stick, then break. This quickly leads to massive oil consumption, bore polishing, then failure.
I believe Top Grove Fill is set at 15%, though many better HDEO's test at less than half the allowable.
I suppose a good synthetic HDEO might slowly clean deposits, but for excessive deposits a proper engine flush is needed.
Jerry