A gas oil composition comprising a gas oil composition selected from the group consisting of the following gas oil compositions (A) to (C) and additives added in accordance with the following Steps 1 and 2:
- [I] gas oil compositions (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, with a sulfur content of 5 ppm by mass or less, an aromatic content of 10 percent by volume or less, an oxygen content of 100 ppm or less, a density of 760 kg/m3 or greater and 840 kg/m3 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 value determined by dividing the total content of normal paraffins having 20 to 30 carbon atoms by the total content of hydrocarbons having 20 to 30 carbon atoms other than the 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;
- [II] gas oil compositions (B) 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, with a sulfur content of 5 ppm by mass or less, an aromatic content of 10 percent by volume or less, an oxygen content of 100 ppm or less, a density of 760 kg/m3 or greater and 840 kg/m3 or less, a 90% distillation temperature of 280° C. or higher and 350° 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 −5° C. or lower, a cold filter plugging point of −20° C. or lower, a pour point of −25° C. or lower, a total content of normal paraffins having 20 to 30 carbon atoms of 2 percent by mass or more and less than 4 percent by mass, a value determined by dividing the total content of normal paraffins having 20 to 30 carbon atoms by the total content of hydrocarbons having 20 to 30 carbon atoms other than the 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 20 to 25 carbon atoms defined by C20P>C21P>C22P>C23P>C24P>C25P;
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- [III] gas oil compositions (C) 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, with a sulfur content of 5 ppm by mass or less, an aromatic content of 10 percent by volume or less, an oxygen content of 100 ppm or less, a density of 760 kg/m3 or greater and 840 kg/m3 or less, a 90% distillation temperature of 280° C. or higher and 350° 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 −3° C. or lower, a cold filter plugging point of −10° C. or lower, a pour point of −12.5° C. or lower, a total content of normal paraffins having 20 to 30 carbon atoms of 4 percent by mass or more and less than 6 percent by mass, a value determined by dividing the total content of normal paraffins having 20 to 30 carbon atoms by the total content of hydrocarbons having 20 to 30 carbon atoms other than the normal paraffins of 0.2 or greater and 0.6 or less, and relations in the content of each of normal paraffins (CnP) having 20 to 25 carbon atoms defined by C20P>C21P>C22P>C23P>C24P>C25P and (C24P-C25P)/C24P>(C22P-C23P)/C22P>(C20-C21P)/C20P;
- (Step 1) a lubricity improver comprising a fatty acid and/or a fatty acid ester is admixed in an amount of 20 mg/L or more and 300 mg/L or less in terms of the active component with the gas oil composition by line-blending, forced-stirring or leaving to stand for a sufficient time;
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- (Step 2) a cold flow improver comprising an ethylene vinyl acetate copolymer and/or a compound with a surface active effect is admixed in an amount of 20 mg/L or more and 1000 mg/L or less in terms of the active component with the gas oil composition by line-blending, forced-stirring or leaving to stand for a sufficient time.