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.