An additive composition, on use in a fuel in a spark-ignition internal combustion engine, controls the formation of sludge and piston varnish. When used in a direct injection spark-ignition internal combustion engine, particulate emissions and deposit formation on intake valves may also be controlled. When used in a port fuel injection spark-ignition internal combustion engine, the port fuel injection valve deposits may be reduced. The additive composition comprises a polyalkylene amine and a hydrocarbyl-substituted hydroxyaromatic compound. The additive compositions may be present in a fuel composition.