Patent ID: 8623103

Claim:
A method of producing a gas oil composition comprising steps of: preparing a gas oil composition (A) comprising an FT synthetic base oil in an amount of 60 percent by volume or more on the basis of the total amount of the gas oil composition (A); and then (Step 1) adding to the composition (A) by line-blending, forced-stirring or leaving to stand a lubricity improver additive comprising a fatty acid and/or a fatty acid ester in an amount of 20 mg/L or more and 300 mg/L or less in terms of the active component on the basis of the total amount of the gas oil composition (A), subsequently (Step 2) adding to the composition (A) by line-blending, forced-stirring or leaving to stand a cold flow improver additive comprising an ethylene vinyl acetate copolymer and/or a compound with a surface active effect in an amount of 20 mg/L or more and 1000 mg/L or less in terms of the active component on the basis of the total amount of the gas oil composition (A), and adding to the gas oil composition (A) by line-blending, forced-stirring or leaving to stand a detergent which is at least one compound selected from the group consisting of a polyether amine compound, a polybutenyl amine compound, and an alkenyl succinimide compound, wherein the detergent is added in an amount of 20 mg/L or more and 500 mg/L or less on the basis of the total amount of the gas oil composition (A); wherein the gas oil composition has a sulfur content of 5 ppm by mass or less, an aromatic content of 1 percent by volume or less, an oxygen content of 100 ppm or less, a density at 15° C. of 760 kg/m 3 or greater and 840 kg/m 3 or less, a 90% distillation temperature of 280° C. or higher and 330° C. or lower and an end point of 360° C. or lower in distillation characteristics, an insoluble content after an oxidation stability test of 0.5 mg/100 mL or less, an HFRR wear scar diameter (WS1.4) of 400 μm or smaller, a cloud point of −15° C. or lower, a cold filter plugging point of −25° C. or lower, a pour point of −32.5° C. or lower, a total content of normal paraffins having 20 to 30 carbon atoms of less than 2 percent by mass, a ratio of a total content of 20 to 30 carbon atom normal paraffins to a total content of hydrocarbons other than the 20 to 30 carbon atom normal paraffins of 0.2 or greater and 0.6 or less, and a relation in the content of each of normal paraffins (CnP) having 15 to 20 carbon atoms defined by C20P<C19P<C18P<C17P<C16P<C15P.