The dispersants are formed by reacting (a) at least one dispersant having at least one primary or secondary amino group and/or at least one hydroxyl group, with (b) at least one polyolefinic compound substituted at each terminal position by a succinic group. Suitable substances for use as reactant (b) include compounds derived from at least one telechelic compound having up to 5000 carbon atoms and at least two terminal methylene groups by reaction with maleic anhydride or the like. The products are deemed to be effective dispersant/detergents for use in fuels and lubricants. In fuels the products are deemed to exhibit the property of inhibiting and/or reducing deposit formation such as intake valve deposits. In crankcase lubricants, the products are deemed to provide desirable viscosity index improving properties.