Fuel additive for improved injector performance

A method of improving the injector performance of a fuel injected engine comprising operating the engine on a fuel composition comprising a major amount of fuel and from about 5 to about 100 ppm by weight based on a total weight of the fuel of a sulfur-free and halogen-free synergistic fuel additive comprising a mixture of:

• (a) an alkoxylated quaternary ammonium compound the formula (R1)nN[(R2O)xH]m, wherein R1 comprises an alkyl group having from 1 to 25 carbon atoms, R2 comprises an alkyl group having from 1 to 4 carbon atoms, n and m are each integers from 1 to 3, provided n+m=4, and at least one R1 has at least 8 carbon atoms, and x is an integer ranging from 1 to 5;
• and
• (b) a hydrocarbyl compound containing a hydrogen-bonding group other than an alkyl hydroxyl group selected from the group consisting of a hydrocarbyl acid;
• hydrocarbyl polyacid;
• hydrocarbyl substituted hydroxybenzene;
• hydrocarbyl substituted succinic diamide, hydrocarbyl substituted succinic acid/amide, hydrocarbyl substituted succinic diacid, hydrocarbyl substituted succinic diester, hydrocarbyl substituted succinic ester/acid, hydrocarbyl substituted succinic amide/ester, hydrocarbyl substituted succinimide;
• a reaction product derived from (i) a hydrocarbyl substituted dicarboxylic acid, anhydride, or ester and (ii) an amine compound or salt thereof of the formula
• wherein R3 is selected from the group consisting of hydrogen and a hydrocarbyl group containing from about 1 to about 15 carbon atoms, and R4 is selected from the group consisting of hydrogen and a hydrocarbyl group containing from about 1 to about 20 carbon atoms, wherein the reaction product (2) on average has less than 1 aminotriazole group per molecule, and mixtures thereof, wherein the hydrocarbyl substituent has a number average molecular weight of from about 100 to about 1500, and wherein a weight ratio of (a) to (b) in the synergistic additive ranges from about 1:5 to about 1:1 and wherein when the synergistic additive(s) is present in the fuel, at least about 60% of the power lost during a dirty up phase of a CEC F98-08 test conducted in the absence of the synergistic additive(s) is recovered.

A method of operating a fuel injected diesel engine comprising combusting in the engine a fuel composition comprising a major amount of fuel and from about 5 to about 100 ppm by weight based on a total weight of the fuel of a sulfur-free and halogen-free synergistic fuel additive comprising a mixture of:

• (a) an alkoxylated quaternary ammonium compound the formula (R1)nN[(R2O)xH]m, wherein R1 comprises an alkyl group having from 1 to 25 carbon atoms, R2 comprises an alkyl group having from 1 to 4 carbon atoms, n and m are each integers from 1 to 3, provided n+m=4, and at least one R1 has at least 8 carbon atoms, and x is an integer ranging from 1 to 5;
• and
• (b) a material containing a hydrogen-bonding group other than an alkyl hydroxyl group selected from the group consisting of a hydrocarbyl acid;
• hydrocarbyl polyacid;
• hydrocarbyl substituted hydroxybenzene;
• hydrocarbyl substituted succinic diamide, hydrocarbyl substituted succinic acid/amide, hydrocarbyl substituted succinic diacid, hydrocarbyl substituted succinic diester, hydrocarbyl substituted succinic ester/acid, hydrocarbyl substituted succinic amide/ester, hydrocarbyl substituted succinimide;
• a reaction product derived from (i) a hydrocarbyl substituted dicarboxylic acid, anhydride, or ester and (ii) an amine compound or salt thereof of the formula
• wherein R3 is selected from the group consisting of hydrogen and a hydrocarbyl group containing from about 1 to about 15 carbon atoms, and R4 is selected from the group consisting of hydrogen and a hydrocarbyl group containing from about 1 to about 20 carbon atoms, wherein the reaction product (2) on average has less than 1 aminotriazole group per molecule, and mixtures thereof, wherein the hydrocarbyl substituent has a number average molecular weight of from about 100 to about 1500, and wherein a weight ratio of (a) to (b) in the synergistic additive ranges from about 1:5 to about 1:1.