Abstract: A continuous method of preparing an overbased calcium sulfonate which comprises repeating the following steps until a desired TBN is obtained, said method comprising: (a) contacting Ca (OH).sub.2 and methanol with a normal calcium sulfonate hydrocarbon solution to solubilize at least a portion of the Ca(OH).sub.2 ; (b) filtering the sulfonate solution to separate and remove the non-solubilized Ca(OH).sub.2 from the solubilized Ca(OH).sub.2 contained in an obtained sulfonate filtrate; (c) treating said sulfonate filtrate with gaseous CO.sub.2 to convert the solubilized CA(OH).sub.2 to solubilized CaCO.sub.3 ; (d) blowing said solubilized CaCO.sub.3 with an inert gas to remove therefrom any excess CO.sub.2 and the aqueous phase generated therein to obtain an overbased sulfonate liquid; (e) adding more of said normal calcium sulfonate solution to said overbased sulfonate liquid and contacting said overbased sulfonate liquid with said non-solubilized Ca(OH).sub.2 and additional fresh Ca(OH).sub.