Diesel fuel composition

A diesel fuel composition comprising a major proportion of a liquid hydrocarbon fuel of diesel fuel boiling range in combination with a minor amount of an N,N-disubstituted organic nitroxide of the formula:

• ##STR2## wherein R.sup.1 and R.sup.2 are independently selected from the group consisting of aryl and substituted aryl of from 6 to 10 carbon atoms and CR.sup.3 R.sup.4 R.sup.5 wherein R.sup.3, R.sup.4 and R.sup.5 each contain from 1 to 15 carbon atoms and are independently selected from the group consisting of hydrocarbyl, aminohydrocarbyl, alkoxyhydrocarbyl, carboxyhydrocarbyl, carboalkoxyhydrocarbyl and cyanohydrocarbyl with the proviso that R.sup.1 and R.sup.2 can be joined to form a 5- or 6-membered ring, and wherein the amount of said nitroxide is effective to increase the cetane number of said liquid hydrocarbon fuel.

A method for increasing the cetane number of a liquid hydrocarbon diesel fuel which comprises mixing said fuel with an N,N-disubstituted organic nitroxide of the formula:

• ##STR3## wherein R.sup.1 and R.sup.2 are independently selected from the group consisting of aryl and substituted aryl of from 6 to 10 carbon atoms and CR.sup.3 R.sup.4 R.sup.5 wherein R.sup.3, R.sup.4 and R.sup.5 each contain from 1 to 15 carbon atoms and are independently selected from the group consisting of hydrocarbyl, aminohydrocarbyl, alkoxyhydrocarbyl, carboxyhydrocarbyl, carboalkoxyhydrocarbyl and cyanohydrocarbyl with the proviso that R.sup.1 and R.sup.2 can be joined to form a 5- or 6-membered ring, and wherein the amount of said nitroxide is effective to increase said cetane number.

A method of operating a compression ignition engine which comprises combusting in said engine a composition which comprises a liquid hydrocarbon fuel in combination with an N,N-disubstituted organic nitroxide wherein the amount of said nitroxide is from about 0.3 to about 2 weight percent of said composition.

A method of operating a compression ignition engine which comprises combusting in said engine a composition which comprises a major proportion of a liquid hydrocarbon fuel in combination with a minor amount of an N,N-disubstituted organic nitroxide of the formula:

• ##STR4## wherein R.sup.1 and R.sup.2 are independently selected from the group consisting of aryl and substituted aryl of from 6 to 10 carbon atoms and CR.sup.3 R.sup.4 R.sup.5 wherein R.sup.3, R.sup.4 and R.sup.5 each contain from 1 to 15 carbon atoms and are independently selected from the group consisting of hydrocarbyl, aminohydrocarbyl, alkoxyhydrocarbyl, carboxyhydrocarbyl, carboalkoxyhydrocarbyl and cyanohydrocarbyl with the proviso that R.sup.1 and R.sup.2 can be joined to form a 5- or 6-membered ring, and wherein the amount of said nitroxide is effective to increase the cetane number of said liquid hydrocarbon fuel.