A method of producing a fuel additive, comprising: producing a first product stream comprising butadiene by passing a feed stream comprising C4 hydrocarbons, including isobutylene, butadiene, 1-butene, 2-butene, cis-2-butene, trans-2-butene, or a combination thereof through a steam cracker; transforming greater than or equal to 90 weight %, preferably greater than or equal to 95 weight percent and more preferably greater than or equal to 96 weight % of the butadiene in the first product stream into a second product stream by passing the first product stream through a first hydrogenation unit comprising three hydrogenation reactors in series, wherein the first hydrogenation reactor comprises a catalyst comprising a noble metal on alumina support and is operated at a temperature of 40 to 70°C and a pressure of 965 to 2758 kPa, the second hydrogenation reactor comprises a catalyst comprising a noble metal on alumina support and is operated at a temperature of 50 to 60°C and a pressure of 965 to 2758 kPa, the third hydrogenation reactor comprises a catalyst comprising a noble metal on alumina support and is operated at a temperature of 60 to 80°C and a pressure of 1724 to 1862 kPa and carbon monoxide is injected into the third reactor, wherein the second product stream comprises 1-butene, 2-butene, n-butane, isobutylene, isobutane, or a combination thereof, and converting the second product stream into the fuel additive by passing the second product stream and a water stream through a fuel additive synthesis unit with an acid catalyst at a temperature of 25 to 300°C and a pressure of 0.25 to 20 MPa, wherein the fuel additive synthesis unit comprises an oscillating baffle reactor, a fixed bed reactor, multitubular reactor, a membrane integrated reactor, a reactive distillation unit, or a combination thereof, wherein the fuel additive comprises trimethylpentane in an amount greater than 0.01 weight percent, preferably greater than or equal to 0.02 weight %, more preferably greater than or equal to 0.1 weight %, based on the total weight of the fuel additive. producing a first product stream comprising butadiene by passing a feed stream comprising C4 hydrocarbons, including isobutylene, butadiene, 1-butene, 2-butene, cis-2-butene, trans-2-butene, or a combination thereof through a steam cracker; transforming greater than or equal to 90 weight %, preferably greater than or equal to 95 weight percent and more preferably greater than or equal to 96 weight % of the butadiene in the first product stream into a second product stream by passing the first product stream through a first hydrogenation unit comprising three hydrogenation reactors in series, wherein the first hydrogenation reactor comprises a catalyst comprising a noble metal on alumina support and is operated at a temperature of 40 to 70°C and a pressure of 965 to 2758 kPa, the second hydrogenation reactor comprises a catalyst comprising a noble metal on alumina support and is operated at a temperature of 50 to 60°C and a pressure of 965 to 2758 kPa, the third hydrogenation reactor comprises a catalyst comprising a noble metal on alumina support and is operated at a temperature of 60 to 80°C and a pressure of 1724 to 1862 kPa and carbon monoxide is injected into the third reactor, wherein the second product stream comprises 1-butene, 2-butene, n-butane, isobutylene, isobutane, or a combination thereof, and converting the second product stream into the fuel additive by passing the second product stream and a water stream through a fuel additive synthesis unit with an acid catalyst at a temperature of 25 to 300°C and a pressure of 0.25 to 20 MPa, wherein the fuel additive synthesis unit comprises an oscillating baffle reactor, a fixed bed reactor, multitubular reactor, a membrane integrated reactor, a reactive distillation unit, or a combination thereof, wherein the fuel additive comprises trimethylpentane in an amount greater than 0.01 weight percent, preferably greater than or equal to 0.02 weight %, more preferably greater than or equal to 0.1 weight %, based on the total weight of the fuel additive.