PURPOSE: To obtain novel dispersants for use in fuel oils and lubricating oils which are comprising adducts of (poly)carboxylic acylation agents and specified heterocyclic polyols and exhibit excellent dispesibility even in a wide variety of the environment.

CONSTITUTION: The objective dispersants are obtained by forming adducts between (A) one or more of mono- or poly-carboxylic acid acyllation agent and (B) heterocyclic polyols shown by the formula [wherein R1 to R4 are each H, alkyl or -CH(OH)R5 (wherein R5 is 1-12C alkyl) [at least one of R1 to R4, however, is -CH(OH)R5]; X and Y are H, 1-10C alkyl]. As a suitable example of the component A, further, long chain hydrocarbyl-substituted succinic acid(anhydride) may be listed.