Dispersant/VI improvers for lubricating oil compositions are disclosed which comprise the reaction product of (a) a copolymer of octadecene-1 and maleic anhydride, the copolymer having a number average molecular weight from greater than 6300 to less than 12000; and (b) a succinimide prepared from a polyamine and an acyclic hydrocarbyl-substituted succinic acylating agent of the formula: ##STR1## wherein X and X.sup.1 are the same or different; provided that at least one of X and X.sup.1 is such that the copolymer can function as a carboxylic acylating agent, and optionally (c) a primary or a secondary hydrocarbyl monoamine or a mixture thereof, preferably an amine of the formula: ##STR2## wherein R.sup.1 is either a saturated or an unsaturated aliphatic hydrocarbyl group, and R.sup.2 is either R.sup.1 or hydrogen, and the total number of carbon atoms in the groups R.sup.1 and R.sup.2 is from 6 to 50, and optionally (d) a compound having at least two primary or secondary amino groups separated by at least three carbon atoms.