This invention provides a base fuel oil, having improved response to lubricity additives, for diesel fuel oil characterized by (1) sulfur content of 0.03 wt % or less, (2) nitrogen content of 35 wt. ppm or less, (3) density of 0.835 g/cm.sup.3 or less and (4) solubility parameter of 7.00 to 8.10, and also provides a diesel fuel oil composition comprising the above base fuel oil incorporated with a lubricity additive.