To provide an additive which has a low emulsifying trend and improves lubricity of effective fuel oil.

The additive comprises (A) 10-95 wt.% of at least one of an oil-soluble amphiphatic medium represented by formulas (I) and/or the formula.R1-X-R2, (wherein, R1 is a 1-50C alkyl, alkenyl, hydroxyalkyl or aromatic residual group; X is NH, HR3, O or S; y is an integer of 1-4 and R2 is H or a 2-10C alkyl residual group containing a hydroxyl group), (B) 5-90 wt.% of at least one of a copolymer comprising (B1) 0.5-15 mole % of a structural unit derived from an olefinically unsaturated compound containing at least one of a free hydroxyl group and (B2) 85-99.5 mole % of a structural unit derived from ethylene, and the copolymer having an average molecular weight (Mw) being 500-100,000 g/mole and OH monohydric 5-300 mg (KOH)/g.