A mixture comprising A) a copolymer comprising from about 70 to about 79% by weight of units derived from ethylene, and having (a) Mw measured by gel permeation chromatography employing polystyrene standard ranging from about 50,000 up to less than 130,000 and/or (f) SSI≦18; (b) density (D) ranging from about 845 to about 895 kg/m3; (c) Mw/ Mn less than 3; (d) melting point (Tm) measured by differential scanning calorimeter ranging from about 15° C. to about 60° C.; and (e) degree of crystallinity≧15%, and B) an amorphous polymer having Mw ranging from about 130,000 to about 1,000,000 having degree of crystallinity≦5%. In one embodiment the density and the melting point of the copolymer A) fulfill the expression Tm≦1.247 D−1037. In another embodiment, the percentage content (E: % by weight) of repeating units derived from ethylene and melting point (Tm: ° C.) of the copolymer A) fulfill the expression 3.44E−206≧Tm. Also, additive concentrates and lubricating compositions comprising the components making up the mixture.