Known event - my foot! How about referencing a legitimate piece of research, like an SAE paper.
Once sludge or oxidation deposits form on surfaces they are unlikely to be signficantly removed by any kind of motor oil. Synthetic-based SI engine oils have about the same detergent and dispersant additive concentrations as mineral-based SI engine oils, so a synthetic would have no more capability to remove hard deposits than a mineral based oil. A HD diesel engine oil (either mineral or synthetic base) might because they have a greater concentration of additives.
These additives are designed to hold oxidized oil molecules in suspension and keep them from depositing on engine surfaces, but once they do, the additives will remove very little.