Abstract: A fuel oil composition containing a minor proportion by weight of a mixture of 20 to 40 wt % of a polyphenol, a sulphurized polyphenol or a hindered phenol and 80 to 60 wt % of a cyclic amide derived from a dicarboxylic acid or anhydride having a hydrogen-and-carbon containing substituent of at least 40 carbon atoms and a polyalkylene polyamine having at least 2 nitrogen atoms and at least 3 carbon atoms (other than carbon atoms in the branched substituents) between the terminal amino groups.A suitable additive is a 70% by weight of the macrocyclic derivative of polyisobutenyl succinic anhydride (MW 1300) and penta propylene hexamine and 30% by weight of 4,4.sup.1 methylene bis (2,6 di tert butyl phenol).

Abstract: Deposit formation on the interior surfaces of structures confining heated hydrocarbon fluids such as refinery units, particularly preheating stages associated with process units such as distillation units, hydrotreaters and thermal crackers, is inhibited by incorporating in the feed stock a small percentage (usually at least about 0.0005 weight percent) of a macrocyclic polyamine formed by cyclodehydration of reaction products of hydrocarbon substituted succinic anhydrides or carboxylic acids with poly 3-amino propyl compounds or by acylation of macrocyclic polyamine and polycyclic polyamines with hydrocarbon substituted succinic anhydride or carboxylic acids. It is desirable in some instances to dissolve additionally in the hydrocarbon fluid such as a feed stock along with the macrocyclic polyamine an oil-soluble dispersant, antioxidant and mixtures thereof.

Abstract: Combinations of an oil-soluble aliphatic copolymer having the property of a nucleator for wax crystallization e.g., an ethylene-vinyl acetate copolymer having a number average molecular weight within the range of 500-50,000, in combination with an oil-soluble hydrocarbyl substituted succinic acid which has been reacted with a nitrogen material to form either an amine salt or an amide or a mixture thereof wherein the hydrocarbyl groups contain 8 to 28, preferably 12 to 22, carbon atoms are useful in improving the cold flow properties of distillate hydrocarbon oils.

Abstract: Oil-soluble aliphatic copolymer having the property of a nucleator for wax crystallization e.g., ethylenevinyl acetate copolymers having a number average molecular weight within the range of 500-50,000, in combination with an oil-soluble derivative of an aromatic copolymer are useful in improving the cold flow properties of distillate hydrocarbon oils.