Abstract: New, highly effective Mannich detergents for use in hydrocarbon fuels are described which reduce engine deposits in spark and compression ignition internal combustion engines. They are Mannich condensation reaction products obtained from reacting: (i) a polyamine having a sterically-hindered primary amino group, (ii) a hydrocarbyl-substituted hydroxyaromatic compound, and (iii) an aldehyde. These Mannich detergent compounds may be dispersed in a liquid carrier to provide a fuel additive concentrate for hydrocarbon engine fuels which effectively control engine deposit formation in intake valves and also other engine regions such as port fuel injectors and combustion chambers.

Abstract: Treated port fuel injectors are disclosed. The treated port fuel injectors have a surface coated with a film which resists or limits deposit formation on the injector surface. The film may be formed by contacting the port fuel injector with: (i) a succinimide compound comprising the reaction product of polyisobutylene-substituted succinic anhydride and a polyamine; (ii) a Mannich base detergent; and (iii) a spark ignition fuel. The treated port fuel injectors may also include a film formed by contacting the port fuel injector with: (i) a Mannich condensation reaction product of a polyamine having a sterically-hindered primary amino group, a hydrocarbyl-substituted hydroxyaromatic compound, and an aldehyde; and (ii) a spark ignition fuel. Methods of forming films on port fuel injector surfaces are also disclosed.