PURPOSE: The titled compositon having good fluidity at a low temp and causing no clogging of a fuel system in the cold district in winter, which is prepd. by adding a pour point depressant to a base gas oil adjusted in a paraffin content to a specified range.

CONSTITUTION: A base oil is obtd. from gas oil prepd. by adjusting the paraffin content of a gas oil fraction obtd. by the atmospheric distillation of a mixed base or paraffin base crude oil, a desulfurized light vacuum gas oil from a mixed base crude oil, etc. to 5.5W12wt%, pref. 6W10wt%. If necessary, partially dewaxed gas oil or paraffin-added gas oil may be used. A pour point depressant usually in an amt. of 100ppmW0.1wt% is added to these base oils to obtain the purpose composition. Fig. 1 shows a relationship of the paraffin content of a base oil to the pour point of the base oil varied by the addition of 500ppm pour point depressant (ECA5920) and Fig. 2 a relationship to CFPP temp. of the base oil.