Carburetor detergents introduced in the early 1950's were capable of keeping carburetors clean and thus prevented engine malfunction caused by this source. However, these detergents generally would not keep PCV valves clean, nor prevent ring belt deposits, and usually did a poor job of cleaning up dirty carburetors on vehicles used in severe services (taxis). Chevron Research has developed new gasoline additives that keep carburetors clean and remove existing deposits from carburetors. These additives also clean up intake manifolds, intake ports, intake valves, and PCV valves. In addition, they assist in keeping oil rings free and clean. Information obtained from numerous field and laboratory engine tests of these new additives in preventing engine deposits and reducing exhaust emissions is discussed in this paper.