Synergistic Low Temperature Flow Improver in Distillate Fuel

1. A petroleum middle distillate fuel which has been improved with respect to its low temperature flow properties by adding thereto a minor amount of a flow improving additive combination of synergistic proportions of: A. a hydrocarbyl succinamic acid material of the formula: ##STR7## wherein R is a straight chain aliphatic hydrocarbon having from 0 to 1 site of olefinic unsaturation and from 14 to 40 carbon atoms and attached at a secondary carbon atom to the succinyl group; one of X.sup.2 and X.sup.3 is --NYY.sup.1, wherein Y and Y.sup.1 are aliphatic hydrocarbyl groups of from 14 to 28 carbon atoms, the other of X.sup.2 and X.sup.3 is of the formula: wherein n varies from 0 to 1, Y.sup.2 and Y.sup.3 are hydrogen, aliphatic hydrocarbon of from 1 to 30 carbon atoms or oxyaliphatic hydrocarbon of from 1 to 30 carbon atoms, and may be taken together with the nitrogen to which they are attached to form a heterocyclic ring of from 5 to 7 annular members; and B. a derivative of an alpha olefin selected from the group consisting of: 1. a dimer of an alpha olefin that has from 16 to 40 carbon atoms; 2. a polymer of dimer (1); 3. An aromatic compound that has been alkylated with dimer (1); and 4. an aromatic compound that has been alkylated with an alpha olefin having from 16 to 50 carbon atoms; said aromatic compound that is alkylated under (3) or (4) being selected from aromatic hydrocarbons having from 1 to 3 benzene rings, from 0 to 3 alkyl groups of from 1 to 20 carbon atoms each, and from 0 to 3 other substituents per ring, said other substituents being selected from the group consisting of COOR, OR, NR.sub.2, F, Cl, Br and NO.sub.2 wherein R is alkyl of 1 to 20 carbon atoms, phenyl or alkylated phenyl having 1 to 2 alkyl groups totalling 1 to 20 carbon atoms; the relative weight ratios of the additives in the combination ranging from 0.01 to 10 parts by weight of B per part by weight of A.

2. The fuel composition of claim 1 wherein B is alkylated diphenyl.

3. The fuel composition of claim 1 wherein B is alkylated diphenyl ether.

4. The fuel composition of claim 1 wherein B is diphenyl alkylated with the dimer of C.sub.19 alpha olefin.

5. The fuel composition of claim 1 wherein B is diphenyl ether alkylated with a mixture of predominantly C.sub.24 -C.sub.28 alpha olefins.

6. The fuel composition of claim 1 wherein B is a dimer of an alpha olefin that has from 16 to 34 carbon atoms.

7. The fuel composition of claim 1 wherein B is alkyl diphenyl or alkyl diphenyl ether having from 1 to 5 alkyl groups per diphenyl group or diphenyl ether group.

8. The fuel composition of claim 1 wherein A is a hydrocarbyl succinamic acid material in which R represents hydrocarbyl groups of mixed C.sub.15 -C.sub.20 cracked wax olefins.

9. The fuel composition of claim 1 wherein in Component A, the said --NYY.sup.1 group is derived from amines selected from the group consisting of: a. di(hydrogenated tallow) amine (C.sub.16 -C.sub.18); b. di(behenyl-arachidyl) amine (C.sub.22 -C.sub.24); c. mixtures of the foregoing.

10. The fuel composition of claim 1 wherein the additive combination is present in a concentration of between about 0.01 and about 3 percent by weight, based on the fuel composition.

11. The fuel composition of claim 1 wherein the middle distillate fuel is a diesel fuel.

12. The fuel composition of claim 1 wherein the middle distillate fuel is a heating oil.

13. A synergistic additive combination that has the property of improving the low temperature filterability of a petroleum distillate fuel when added thereto which comprises: A. a hydrocarbyl succinamic acid material of the formula: ##STR8## wherein R is a straight chain aliphatic hydrocarbon having from 0 to 1 site of olefinic unsaturation and from 14 to 40 carbon atoms and attached at a secondary carbon atom to the succinyl group; one of X.sup.2 and X.sup.3 is --NYY.sup.1, wherein Y and Y.sup.1 are aliphatic hydrocarbyl groups of from 14 to 28 carbon atoms, the other of X.sup.2 and X.sup.3 is of the formula: wherein n varies from 0 to 1, Y.sup.2 and Y.sup.3 are hydrogen, aliphatic hydrocarbon of from 1 to 30 carbon atoms or oxyaliphatic hydrocarbon of from 1 to 30 carbon atoms, and may be taken together with the nitrogen to which they are attached to form a heterocyclic ring of from 5 to 7 annular members; B. a derivative of an alpha olefin selected from the group consisting of: 1. a dimer of an alpha olefin that has from 16 to 40 carbon atoms; 2. a polymer of dimer (1); 3. an aromatic compound that has been alkylated with dimer (1); and 4. an aromatic compound that has been alkylated with an alpha olefin having from 16 to 50 carbon atoms; said aromatic compound that is alkylated under (3) or (4) being selected from aromatic hydrocarbons having from 1 to 3 benzene rings, from 0 to 3 alkyl groups of from 1 to 20 carbon atoms each, and from 0 to 3 other substituents per ring, said other substituents being selected from the group consisting of COOR, OR, NR.sub.2, F, Cl, Br and NO.sub.2 wherein R is alkyl of 1 to 20 carbon atoms, phenyl or alkylated phenyl having 1 to 2 alkyl groups totalling 1 to 20 carbon atoms; the relative weight ratios of the additives in the combination ranging from 0.01 to 10 parts by weight of B per part by weight of A.

14. An additive concentrate comprising about 3 to 60 wt. % of the additive combination of claim 13 in a hydrocarbon oil.