A metal-working fluid concentrate for use as an oil-in-water emulsion, comprising: a base oil component in an amount of 5-90 wt. %, based on the total weight of the concentrate. an emulsifier selected from any of the conventional anionic, cationic, nonionic, or amphoteric surfactants, in an amount of 0.1 to 15 wt. %. at least an additive selected from saponifiers, pH buffers, preservatives, extreme pressure EP additives, corrosion inhibitors, anti-wear agents, metal deactivators, defoamers, anti-rust agents, deodorants, dyes, fungicides, bacteriocides, antioxidants, emulsion stabilizers, dispersion stabilizers in an amount of 0.1 to 15 wt. %. wherein the base oil component contains at least 50% by weight of a decarboxylated rosin acid (DCR) based on the total weight of the base oil component, and remainder being oil selected from naphthenic, paraffin, bio-based oil and mixtures thereof, and wherein the DCR has: a m/z (mass/charge) of 220-280 as measured by GC-FID-MS, an oxygen content of < 5% as obtained from elemental analysis, an acid value of < 10 mg KOH/g as measured according to ASTM E28-18; and wherein the DCR comprises: > 50 % by weight as tricyclic and polycyclic compounds having 18-20 carbon atoms as measured by GC-FID-MS, > 55 % by weight of tricyclic compounds as aromatic and cycloaliphatic as measured by GC-FID-MS, < 45 % by weight of tricyclic compounds as reactive double bond (C=C group) as measured by GC-FID-MS. a base oil component in an amount of 5-90 wt. %, based on the total weight of the concentrate. an emulsifier selected from any of the conventional anionic, cationic, nonionic, or amphoteric surfactants, in an amount of 0.1 to 15 wt. %. at least an additive selected from saponifiers, pH buffers, preservatives, extreme pressure EP additives, corrosion inhibitors, anti-wear agents, metal deactivators, defoamers, anti-rust agents, deodorants, dyes, fungicides, bacteriocides, antioxidants, emulsion stabilizers, dispersion stabilizers in an amount of 0.1 to 15 wt. %. wherein the base oil component contains at least 50% by weight of a decarboxylated rosin acid (DCR) based on the total weight of the base oil component, and remainder being oil selected from naphthenic, paraffin, bio-based oil and mixtures thereof, and wherein the DCR has: a m/z (mass/charge) of 220-280 as measured by GC-FID-MS, an oxygen content of < 5% as obtained from elemental analysis, an acid value of < 10 mg KOH/g as measured according to ASTM E28-18; and a m/z (mass/charge) of 220-280 as measured by GC-FID-MS, an oxygen content of < 5% as obtained from elemental analysis, an acid value of < 10 mg KOH/g as measured according to ASTM E28-18; and wherein the DCR comprises: > 50 % by weight as tricyclic and polycyclic compounds having 18-20 carbon atoms as measured by GC-FID-MS, > 55 % by weight of tricyclic compounds as aromatic and cycloaliphatic as measured by GC-FID-MS, < 45 % by weight of tricyclic compounds as reactive double bond (C=C group) as measured by GC-FID-MS. > 50 % by weight as tricyclic and polycyclic compounds having 18-20 carbon atoms as measured by GC-FID-MS, > 55 % by weight of tricyclic compounds as aromatic and cycloaliphatic as measured by GC-FID-MS, < 45 % by weight of tricyclic compounds as reactive double bond (C=C group) as measured by GC-FID-MS. <EOS>