Abstract: Compounds of general formula (I) wherein X and Y are the same or different and are selected from the group consisting of SO.sub.3 (--), --CO--, --C(O)O(--), --R.sup.4 --C(O)O--, --NR.sup.3 C(O)--, --R.sup.4 O--, --R.sup.4 --C(O)O--, --R.sup.4 -- and --NC(O)--, R.sup.4 being --(CH.sub.2).sub.m -- where m is from 0 to 5 and R.sup.3 is defined below; X.sup.1 and Y.sup.1 are the same or different and are selected from the group consisting of (a), R.sup.1 and R.sup.2 being independently selected from the group consisting of alkyl, alkoxy alkyl or polyalkoxyalkyl groups that contain at least 10 carbon atoms in their main chain, and R.sup.3 being a hydrocarbyl group, each R.sup.

Abstract: A crude oil or fuel oil composition comprises a major proportion by weight of a crude oil or a fuel oil and a minor proportion by weight of a polycarbonate containing the group ##STR1## where n is an integer of two or more and A is an alkylene, aralkylene or arylene radical, provided the alkylene group can be interrupted by one or more hetero atoms or by one or more carboxylic ester, carbamoyl, urethane, urea or tertiary amino groups. A typical polycarbonate has the formula ##STR2## where R are C.sub.10 to C.sub.30 alkyl groups.