To obtain a superalkalinized alkylaryl sulphonate useful as detergent and dispersant additives for lubricating oils, having a specific radical bound to a linear alkyl chain and capable of preventing e.g. formation of skin on the surface during storage, deterioration of anticorrosive property or generation of turbid appearance.

This sulphonate comprises an aryl other than a phenyl, e.g. a tolyl, xylyl, O-xylyl, ethyl-phenyl or cumenyl and a 14-40C normal alkali chain, wherein an aryl sulphonate radical of alkaline earth metal is fixed in the positions 1 or 2 of the linear alkaline chain in a molar proportion of 0 to 13%. The sulphonate is obtained by sulphonating an alkylaryl hydrocarbon substituted with an aryl other than a phenyl in a molar proportion of 0 to 13% and by reacting the obtained sulphonic acid with an excessive alkaline earth base.