Hydrocarbon oil pour point depressants (I) comprising polyketones (II) prepared by copolymerisation of alpha-olefin (III) and carbon monoxide in presence of free radical catalysts (IV). (II) have no. mol. wts. 500-5000 (pref. 1000-3000) and are used in amounts of 0.001-2.0% wt based on hydrocarbon oil depending on type of oil to be treated. Amounts of (III) and CO in (II) are 80-95% wt and 5-20% wt respectively. (I) is suitable for use with wide range of hydrocarbon oils, especially for fuels and as wax crystal modifiers.
