Abstract: The present invention concerns a process for preparing a basic additive for lubricating oils having an antiwear and detergent effect, the additive thus obtained and a lubricating composition containing the additive. The process consists of contacting an amino-acid in solution or in dispersion in the oil with a detergent, an alkaline-earth metal derivative, carbon dioxide in diluent oil, a hydrocarbon-based solvent, and a polar solvent in the presence of a nitrogen-based basic derivative.

Abstract: This invention concerns a process for preparing very fluid overbased additives having a high basicity, by contacting an alkaline-earth metal derivative and at least one surfactant with carbon dioxide in a diluent oil and a hydrocarbon-based solvent in the presence of an oxygen-based promoter and a nitrogen-based promoter wherein the carbonation time is comprised between an initial point Po corresponding to the beginning of the temperature plateau of the exothermic reaction and the end point of the carbonation which corresponds to a sudden drop of the alkaline value, the additives according to the invention being utilized in lubricating oils and fuels.