An overbased calcium sulfonate grease composition comprising a reduced amount of overbased calcium sulfonate, added calcium carbonate, base oil, one or more converting agents, and one or more complexing acids if a complex grease is desired. The calcium sulfonate grease composition improves thickener yield and expected high temperature utility as demonstrated by dropping point. The calcium carbonate may be used to react with complexing acids when making a complex grease, such that the addition of calcium oxide or calcium hydroxide is not required. A method of making the composition comprising the steps of mixing the overbased calcium sulfonate and base oil, adding the calcium carbonate, adding one or more converting agents, and adding one or more complexing acids. All or a portion of one or more of the complexing acids may be added with or prior to the one or more converting agents.