Dispersant detergent additives for lubricating oils prepared by neutralization, carboxylation, sulfurization-overalkalinization, carbonation, distillation, filtering and degassing from alkyl phenols containing 35-85% by weight of linear alkyl substituents. The process does not require, during the neutralizing phase, the presence of a third solvent, which, by forming an azeotropic mixture with water promotes the elimination of water arising from the neutralizing reaction. The additives of the invention have improved stability to hydrolysis and improved dispersion properties, improved compatibility and improved foaming properties.