Deposits that accumulate in the critical areas of carburetors can adversely affect the designed metering characteristics. Since this can cause an increase in vehicle exhaust emissions, it is important that these deposits be minimized. Fuel additives provide an effective means of cleaning carburetors and keeping them clean. Thirteen commercial and experimental additives of different chemical composition were screened in laboratory engine tests, and four of these were selected for further evaluation in vehicles operated in consumer type service. The detergency action of the additives resulted in reduced carburetor deposits, reduced exhaust emissions, and improved fuel economy. In most cases, there was an additive concentration effect, in which effectiveness increased with increased concentration. The laboratory engine tests were useful to evaluate the carburetor detergency characteristics of the additives prior to initiating more extensive field service tests on the most promising ones. A directional correlation was obtained between the laboratory engine tests and the vehicle tests in consumer type service.