Method for reducing intake valve deposits

Method for reducing intake valve deposits in a spark ignition internal combustion engine which is fuelled with a gasoline fuel composition wherein the method comprises introducing into the engine an aqueous based composition, wherein the aqueous based composition comprises (i) from 58 to 98 vol % water, based on the total volume of components (i), (ii) and (iii), (ii) from 1 vol % to 40 vol % of freezing point suppression agent, based on the total volume of components (i), (ii) and (iii), selected from alcohols, glycols, dialkyl carbamates, and mixture thereof, (iii) from 1 vol % to 10 vol % of surfactant, based on the total volume of components (i), (ii) and (iii), wherein the surfactant is a nonionic surfactant not encompassing an amine compound according to (iv), and (iv) an amine compound selected from polyalkylene based amine compounds, polyetheramine compounds, and mixtures thereof, in a blending amount of from 100 ppmw to 1000 ppmw, based on parts of amine compound per million weight parts of components (i), (ii) and (iii) in combination,

• wherein the aqueous based composition is stored in a separate tank and introduced into the engine via an injection system and is injected separately from the fuel in such a way that it creates a washing action on the back of intake valves of said engine by injection into the cylinder, onto the valves or into the manifold of said engine.