”Detergent” motor oil is a phrase applied to late-1950s/early 1960s automotive oils, and those terms have been loosely (erroneously) applied to aviation.You explained why aviation oil, containing dispersants rather than detergents, is advantageous in an aircraft engine, because it doesn't result in metallic residues.
Do you know what the advantages (if any) are of detergents? Are they simply cheaper or do they have some performance advantage within the operational envelope of a non-aviation engine?
Engine oils are refined/packaged to be without additives of any kind….(so-called “mineral” oils)… which are typically used in older equipment because “detergent-additives” have a cleaning effect that can dislodge caked/solidified residues which remain in-situ on stationary engine components such as crankcase and sump walls, non-moving items and areas which do not directly require lubrication…. the majority of the insides of engines.
Pistons, bearings, bushings, gears, impellers, etc. make physical contact with other moving parts and naturally “clean” those areas they contact. “Detergents” can adversely affect sludge/residues in older engines by dissolving and re-distributing those contaminates and can actually contribute to damage when suddenly released into the lubrication-stream. That is why it is recommended not to introduce “detergent oils” into equipment which has long-operated on non-detergent oil.
An engine which is “New” or newly-rebuilt is often “broken in” on mineral oils because no anti-friction additives which can prolong or prevent “break-in” are present in “mineral” oil. (Synthetics are often also avoided for break-in, but not always, depending upon manufacturing tolerances.)
The advantages of a “detergent” oil in a non-aviation engine which has not been long-operated without detergent oil …is that the engine interior will remain cleaner as contaminants are kept in suspention until the pump can push them into/thru the filter to be captured. However, not all contaminants are solids…so filters don’t capture them. Those soluble contaminates are removed at the next oil-drain period.
Aircraft operating in lower atmospheric pressures (altitudes) can develop a detonation problem if metallic residues in the combustion chambers “glow” and cause pre-ignition, and any existing sludge might be freed by the use of detergents…. So aviation oils do not use them, instead relying upon “dispersants” which bring the contaminates to the filters for removal.
HOpe that helps.