Abstract: The octane requirement increase phenomenon in a spark ignition internal combustion engine is controlled by introducing with the combustion charge a fuel composition containing an octane requirement increase-inhibiting amount of a combination of compounds, the combination comprising a first compound being (1) a gasoline soluble amide and (2) a second compound being a gasoline soluble ketone. Usually the first and second compounds are each added to the fuel in an amount between about 0.001 and 3 weight percent of the fuel. In particular, the combination of N,N-dibutyl formamide and either benzophenone or methylcyclohexanone provides an effective octane requirement increase-inhibiting additive for unleaded gasoline.

Abstract: The octane requirement increase phenomenon in a spark ignition internal combustion engine is controlled by introducing with the combustion charge a fuel composition containing an octane requirement increase-inhibiting amount of a compound selected from the group consisting of fused aromatics having at least 2, preferably between 3 and 5, aromatic rings with no heteroatoms substituted in the rings. The polynuclear aromatics can be either unsubstituted or substituted with groups other than an alkyl group. Usually the polynuclear aromatic is added to the fuel in an amount between about 0.1 and 5.0 weight percent of the fuel. In particular, anthracene and phenanthrene, and their non-alkyl derivatives, provide effective octane requirement increase-inhibiting additives for unleaded gasoline.

Abstract: The octane requirement increase phenomenon in a spark ignition internal combustion engine is controlled by introducing with the combustion charge a fuel composition containing an octane requirement increase-inhibiting amount of a combination of compounds, the combination comprising (1) a gasoline soluble amide and (2) a gasoline soluble ketone. Usually the two compounds are each added to the fuel in a concentration between about 0.001 and 3 weight percent of the fuel. In particular, the combination of N,N-dibutyl formamide and either benzophenone or methylcyclohexanone provides an effective octane requirement increase-inhibiting additive for unleaded gasoline.

Abstract: The octane requirement increase phenomenon in a spark ignition internal combustion engine is controlled by introducing with the combustion charge a fuel composition containing an octane requirement increase-inhibiting amount of a compound selected from the group consisting of fused aromatics having at least 2, preferably between 3 and 5, aromatic rings with no heteroatoms substituted in the rings. Usually the polynuclear aromatic is added to the fuel in an amount between about 0.1 and 5.0 weight percent on the fuel. In particular, anthracene and phenanthrene, provide effective octane requirement increase-inhibiting additives for unleaded gasoline.

Abstract: The control of the octane requirement increase phenomenon in an internal combustion engine is achieved by introducing into an internal combustion engine, having manifold and/or combustion surfaces which inhibit the formation of engine deposits, along with the combustion charge, a fuel composition containing an octane requirement increase-inhibiting amount of (a) an oil-soluble iron compound and (b) carboxylic acids and/or ester derivatives thereof. In particular the esters of a tertiary alcohol and an unsubstituted, mono-carboxylic acid having at least two carbon atoms, e.g., t-butylacetate, in combination with dicyclopentadienyl iron provides an effective octane requirement increase-inhibiting additive for said internal combustion engine. Preferably the manifold and combustion surfaces of said internal combustion engine are coated with a low density alumina or zirconia coating. More preferably said alumina or zirconia coating further comprises a carbon gasification catalyst, e.g.