Fuel additive systems, compositions, and methods.

A method of reducing a NOx produced by combusting a combustible fuel composition in a combustion engine comprising at least one combustion chamber and at least one exhaust port, the method comprising:

• (a) contacting each combustion engine chamber with the combustible fuel composition, the combustible fuel composition comprising:
• (i) a liquid fuel selected from the group consisting of aliphatic hydrocarbons, gasoline, jet fuel, diesel, biodiesel, and combinations thereof;
• and
• (ii) an additive comprising at least one compound having a structure according to Formula I:
• R1-R2 (I)
• wherein:
• R1 is selected from the group consisting of HO, EtO, PrO, BuO, i-PrO, and t-BuO;
• R2 is (C═O)R3;
• and
• R3 is selected from the group consisting of C1-18 alkyl, C1-6 alkyl alcohol, C2-18 monounsaturated alkyl, and C4-18 polyunsaturated alkyl,
• wherein each stereoisomer is selected from the group consisting of E, Z, R, S, and a combination thereof,
• wherein the liquid fuel comprises at least one of a jet fuel, a diesel fuel, a gasoline, a naphtha, an ethanol, a coal tar, a liquefied petroleum gas, a compressed natural gas, and a butanol, and
• wherein the jet fuel comprises at least one of aviation turbine fuel, Jet A, Jet A-1, Jet A-2, Jet A-3, Jet A-4, Jet A-5, Jet A-6, Jet A-7, Jet A-8, Jet B, Jet Propellant-4, Jet Propellant-5, Jet Propellant-7, and Jet Propellant-8,
• (b) combusting the combustible fuel composition to produce an exhaust gas;
• and
• (c) venting at least a portion of the exhaust gas,
• wherein the exhaust gas includes at the exhaust port up from about 2% to about 98% of the NOx in a reference exhaust gas produced by combusting the same combustible fuel composition that lacks the additive.