NOVELTY - Additive concentrate comprises a functionalized diblock copolymer in mixture with an organic liquid miscible with fuel or oil. The copolymer comprises first block consists of a chain of ethylenic structural units, optionally interrupted by at least one structural units derived from 1-alkene co-monomers higher than ethylene and second block comprises a chain of structural units derived from at least one alpha , beta -unsaturated monomers e.g. styrene or acrylate compounds. The first and second blocks are terminally joined by substituted phenyl alkyl linkage (I).    USE - The additive concentrate is useful in a fuel or oil composition to improve the cold flow behavior of the base fuel or oil during cold storage or use, where the base fuel is a diesel fuel, heating oil or lubricating oil (all claimed).    DETAILED DESCRIPTION - Additive concentrate comprises a functionalized diblock copolymer in mixture with an organic liquid miscible with fuel or oil. The copolymer comprises 2 polymeric blocks. The first block consists of a chain of ethylenic structural units, optionally interrupted by at least one structural units derived from 1-alkene co-monomers higher than ethylene and the second block comprises a chain of structural units derived from at least one alpha , beta -unsaturated monomers comprising styrene, substituted styrene, acrylate, methacrylate or diene compounds. The first and second blocks are terminally joined by substituted phenyl alkyl linkage of formula (I), where the aromatic ring substituent joined to the second block is positioned meta or para to the aromatic ring substituent joined to the first block.    R = alkyl or aryl; and    R1a = H or alkyl.    INDEPENDENT CLAIMS are also included for:    (1) a fuel or oil composition comprising a base fuel or oil derived from at least one petroleum, animal, vegetable or synthetic sources, the base fuel contains at least one n-alkyl, iso-alkyl or n-alkenyl-substituted compounds exhibiting a tendency to crystallize from the base fuel or oil in cold storage or use thus adversely affecting the cold flow behavior of the base fuel or oil, and the additive concentrate, which is present in the composition to improve the cold flow behavior of the base fuel or oil during cold storage or use;    (2) improving the cold flow behavior of fuel or oil composition derived from at least one petroleum, animal, vegetable or synthetic sources and contains at least one n-alkyl, iso-alkyl or n-alkenyl-substituted compounds exhibiting a tendency to crystallize from the base fuel or oil in cold storage or use thus adversely affecting the cold flow behavior of the base fuel or oil, comprising determining the cold flow behavior of the base fuel or oil in question and the improvement that is required, determining the amount of the additive concentrate necessary to effect the desired improvement in cold flow behavior and treating the base fuel or oil with that amount of the additive concentrate;    (3) the functionalized diblock copolymer;    (4) manufacturing the functionalized diblock copolymer comprising 2 polymeric blocks, comprising polymerizing ethylene and optionally at least one 1-alkene co-monomer higher than ethylene in the presence of a metallocene catalyst system to form a first polymer block, being a chain consisting of ethylenic structural units optionally bearing pendent alkyl groups originating from 1-alkene comonomers, the reaction is carried out in solution at temperature of at least 50 degrees C in the presence of substituted phenyl alkylene compounds of formula (Ia) in a reaction vessel pressurized with hydrogen gas, where in the course or reaction, (Ia) is terminally incorporated onto the first polymer block resulting in the formation of a terminally unsaturated intermediate of formula (II), recovering (II) from the reaction mixture and reacting (II) at its terminal double bond in a subsequent polymerization reaction to form a second polymer block to yield diblock polymer;    (5) the isolated intermediate (II), where the aromatic ring substituent -C(R)=CH2 is positioned meta or para to the substituent joined to the first block; and    (6) anionic intermediate substituted phenyl alkyl compounds of formula (III), where the aromatic ring substituent -C-(R)-CH2(R1a) is positioned meta or para to the aromatic ring substituent joined to the first block and C- is metallated carbanionic site.    M+ = metal cation, preferably lithium cation.