Abstract: A process for preparing highly basic magnesium sulfonates useful as lubricants including (a) forming an admixture of an oil-soluble sulfonic acid, a previously overbased magnesium sulfonate having a TBN in excess of about 200, a lower alkanol, and a volatile solvent, (b) heating the admixture to neutralize the acid, (c) cooling the first admixture and then forming a second admixture by adding magnesium oxide, naphthenic acid, a lower alkanol and a diluent oil, (d) carbonating the second admixture with carbon dioxide, while simultaneously adding water and ammonia or an ammonium compound as promoters, during the addition of about the first 25% of the carbon dioxide, (e) heating the carbonated solution to remove water and the lower alkanol, (f) further carbonating the solution for a short time between 180.degree. F. and 220.degree. F.