AbstractColloidal dispersions of calcium carbonate stabilised by overbased sulphonates are used as lubricant additives to provide detergency, remove acidity, and prevent wear. In the present work various overbased sulphonate compounds have been analysed using X‐ray diffraction (XRD). The amorphous overbased sulphonates studied displayed broad diffraction patterns while the crystalline overbased sulphonates gave well‐defined diffraction patterns, correlating with the particle size. The XRD distances of the series of Mg, Ca, and Ba overbased sulphonates shifted to greater values and displayed a clear correlation (r = 0.98) with the ionic radius of the cations u