Leaves an ash residue when combusted. Not used in airplane engine oils. The tempature differences allow the ash to break up into small deposits, and go into the exhaust or blow by the rings into the crankcase and lubricants. In an airplane engine, the pistons are operating continuously at a single speed, and therefore do not go through heating and cooling cycles, so the ash deposits would not break up. Red Line Racing Oils are low detergent.
Detergent is left out because ash can cause detonation.
Dispersants are ashless detergents, which complex low temperature combustion byproducts. Dispersants keep partially oxidized particles in suspension, and help keep the engine clean. Dispersants can come apart in exterme high temperature. Average oil filter is a 20 micron filter. Could go down to 1 micron.