Abstract: This invention relates to a process for the production of overbased metal salts of hydrocarbyl dithiophosphoric acid comprising:a) treating hydrocarbyl dithiophosphoric acid with an effective amount of phosphorus sulfide at a temperature within the range of from about 50.degree. to about 200.degree. C.; andb) neutralizing the treated hydrocarbyl dithiophosphoric acid with an amount of metal oxide;whereby the effective amount of phosphorus sulfide is sufficient to form a basic metal salt of the dithiophosphoric acid having a base metal to phosphorus ratio within the range of from about 1.15:1 to about 1.3:1.

Abstract: This invention relates to a process for preparing an overbased metal salt of hydrocarbyl dithiophosphoric acid comprising neutralizing hydrocarbyl dithiophosphoric acid with an amount of metal oxide sufficient to form said overbased metal salt of hydrocarbyl dithiophosphoric acid, which metal oxide has a surface area of no less than about 4 m.sup.2 per gram up to about 12 m.sup.2 per gram and whereby the overbased metal salt of hydrocarbyl dithiophosphoric acid thus formed has a base metal to phosphorus weight ratio within the range of greater than about 1.2:1 up to about 1.3:1.