A naphthenic acid corrosion inhibiting composition comprising a chemical mixture of: i) corrosion inhibiting amount of an olefin phosphorus sulphur compound A; and ii) corrosion inhibiting amount of an organophosphorus compound selected from the group consisting of: a) compound B, and b) compound C; wherein said olefin phosphorus sulphur compound A is produced by reacting olefin with phosphorus pentasulphide in presence of catalytic amount of sulphur to form a reaction mixture, wherein molar ratio of said olefin to said phosphorus pentasulphide is between 1:0.05 to 1:1.5, preferably 1:1; wherein said olefin is polyisobutylene; wherein said compound B is a phosphate ester of the formula: wherein R 1 and R 2 are each independently selected from the group consisting of hydrogen and moieties having from one to thirty carbon atoms, and R 3 is a moiety having from one to thirty carbon atoms; and wherein said compound C is an aryl containing phosphite compound excluding nitrogen having a structure selected from the group consisting of: wherein R 1 , R 2 and R 3 are C 6 to C 12 aryl or alkyl and at least one R group is an aryl radical; and wherein said corrosion inhibiting amount of said mixture of said compound A, and said one of the organophosphorus compound selected from the group consisting of said compound B, and said compound C is from 1 ppm to 5000 ppm. i) corrosion inhibiting amount of an olefin phosphorus sulphur compound A; and ii) corrosion inhibiting amount of an organophosphorus compound selected from the group consisting of: a) compound B, and b) compound C; wherein said olefin phosphorus sulphur compound A is produced by reacting olefin with phosphorus pentasulphide in presence of catalytic amount of sulphur to form a reaction mixture, wherein molar ratio of said olefin to said phosphorus pentasulphide is between 1:0.05 to 1:1.5, preferably 1:1; wherein said olefin is polyisobutylene; wherein said compound B is a phosphate ester of the formula: wherein R 1 and R 2 are each independently selected from the group consisting of hydrogen and moieties having from one to thirty carbon atoms, and R 3 is a moiety having from one to thirty carbon atoms; and wherein said compound C is an aryl containing phosphite compound excluding nitrogen having a structure selected from the group consisting of: wherein R 1 , R 2 and R 3 are C 6 to C 12 aryl or alkyl and at least one R group is an aryl radical; and wherein said corrosion inhibiting amount of said mixture of said compound A, and said one of the organophosphorus compound selected from the group consisting of said compound B, and said compound C is from 1 ppm to 5000 ppm. a) compound B, and b) compound C; wherein R 1 and R 2 are each independently selected from the group consisting of hydrogen and moieties having from one to thirty carbon atoms, and R 3 is a moiety having from one to thirty carbon atoms; and wherein said compound C is an aryl containing phosphite compound excluding nitrogen having a structure selected from the group consisting of: wherein R 1 , R 2 and R 3 are C 6 to C 12 aryl or alkyl and at least one R group is an aryl radical; and wherein said corrosion inhibiting amount of said mixture of said compound A, and said one of the organophosphorus compound selected from the group consisting of said compound B, and said compound C is from 1 ppm to 5000 ppm. wherein R 1 , R 2 and R 3 are C 6 to C 12 aryl or alkyl and at least one R group is an aryl radical; and wherein said corrosion inhibiting amount of said mixture of said compound A, and said one of the organophosphorus compound selected from the group consisting of said compound B, and said compound C is from 1 ppm to 5000 ppm. <EOS>