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We report on a comprehensive fuel additive study where two different detergent chemistry types, Mannichs and polyetheramines, are ranked with regard to injector deposit control in a research direct-injected gasoline (DIG) engine. The engine used was a conventional dual-sparkplug, 2.2-liter Nissan engine modified for direct injection using one of the sparkplug holes. The engine was run under 20% rich conditions to accelerate injector deposit formation. The two detergent chemistry types are shown to perform quite differently with the Mannichs showing superior performance. The Mannich detergent chemistries can reduce the DIG injector flow loss after using Howell EEE fuel from a high of 11.23% to a low of 3.14% whereas the best polyetheramine detergent chemistry tested reduced it to 8.17%. One of the Mannichs was further tested in a year 2000 specification gasoline with 150 ppm sulfur, and a North American type gasoline with 420 ppm sulfur.