Disclosed herein is a process for preparing a salt of a sulfurized alkyl-substituted hydroxyaromatic composition having a reduced content of unsulfurized alkyl-substituted hydroxyaromatic compound and its unsulfurized metal salt. The process involves the steps of: (a) providing a composition comprising (i) a salt of a sulfurized alkyl-substituted hydroxyaromatic compound; (ii) an unsulfurized alkyl-substituted hydroxyaromatic compound and (iii) an unsulfurized metal salt of the alkyl-substituted hydroxyaromatic compound; wherein the alkyl-substituted hydroxyaromatic compound is derived from alkylation of a hydroxyaromatic compound with one or more olefins comprising C9 to C18 oligomers of monomers selected from propylene, butylene or mixtures thereof; (b) protonating the unsulfurized metal salt of the alkyl-substituted hydroxyaromatic compound with an effective amount of an acidic compound capable of protonating the unsulfurized metal salt of the alkyl-substituted hydroxyaromatic compound; and (c) removing th
