TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Ring Group: The ring group is a hydrocarbyl group free of heteroatoms, preferably cyclopropyl group or cyclobutyl group, or an epoxy group or an oxetane group.The compound has 2 or more strained ring groups such as fused bicyclo group or spirocyclic groups.The ring contains at least 2 carbon atoms and not more than 2 heteroatoms selected from oxygen and nitrogen, preferably oxygen.Preferred Compound: The compound is bicyclopropyl or lower 1-5C alkyl mono or di-substituted bicyclopropyl compound.Preferred Composition: The fuel composition further comprises a hydroxylamine having formula Ra(N(Rb)OH)n (I), a hydroxylamine having formula Rc(N(OH)Rd)xN(OH)Rc (II), a hydroxylamine salt selected from nitrates, sulfonates, carbonates, sulfates and carboxylates, a nitro compound and oxygenates selected from lower alkanol and ethers, and compound selected from dispersants, combustion modifiers, lubricity agents, cold flow improvers, fluidizers, surfactants, and/or corrosion inhibitors.Ra, Rb = H, primary hydrocarbyl, or secondary hydrocarbyl;n = 1-30;Rc = H or hydrocarbyl;Rd = lower alkylene; andx = 1-29.Preferred Fuel: The fuel is gasoline satisfying specification ASTM D-4814, diesel fuel satisfying specification ASTM D-975 or heating oil satisfying specification ASTM D-396. The fuel is a mixture of hydrocarbon fuel such as gasoline and lower alkanol.The fuel is biomass fuel such as biodiesel fuel and vegetable oil.The fuel is an emulsified mixture of water and hydrocarbon fuel and the emulsion comprises water in fuel emulsion or fuel in water emulsion.The emulsion is a microemulsion and water is present in an amount of 0.1-5 wt.% or 2-30 wt.% of the fuel composition.The emulsified fuel is an invert emulsion.The fuel is a synthetic fuel obtained by Fischer-Tropsch process such as hydrocarbon fuel.Preferred Combustion Characteristics: The combustion characteristics are reduced particulate emissions, reduced nitrogen oxide emissions, improved fuel efficiency and reduced hydrocarbon emissions. SPECIFIC COMPOUNDS - The compound is dicyclopropyl ketone, dicyclobutyl ketone, cyclopropyl methanol, cyclobutyl amine, cyclobutyl hydroxylamine, 3,3-dimethyloxetane and 1-methoxy-2-methylpropylene oxide, preferably 3,3-dimethoxyoxetane.    EXAMPLE - 3,3-dimethoxyoxetane (5000 ppm) was blended into gasoline and a fuel composition was obtained.