A field test was conducted in order to evaluate the effect of detergent additives on vehicles representative of the Venezuelan automotive fleet using a Venezuelan gasoline, in terms of carburetor deposits formation, fuel economy, and exhaust emissions. The field test was performed in twenty carbureted vehicles of two different models that were divided into three groups. Two groups used gasoline with detergent additives evaluated with the supplier recommended dose. The third group used a base gasoline without additive, representative of those provided for the internal market by all refineries in the country (95 RON). This was the same base gasoline used for the additized groups. Each car was chosen so that all cars of the same model had similar carburetor deposit evaluation and fuel economy measurements. The design technologies of these car models (engine displacement, configuration, fuel admission systems, etc.) constitute the current technologies present in more than 80 % of the cars in the Venezuelan automotive fleet. The test was developed in three phases. Phase I consisted in the accumulation of 2500 kilometers by all the vehicles using gasoline without additive. Phase II was the accumulation of 10000 kilometers on clean up dose for the two groups of vehicles using additive, and Phase III was the accumulation of 10000 kilometers on keep clean dose for the same two groups of vehicles. Exhaust emissions (grams/kilometer of HC, CO, CO2 and NOx) and fuel economy (kilometers/liter) were measured on a chassis dynamometer at the start of the test, every 2500 kilometers, and at the end of the test. The procedure used for emissions and fuel economy measurements is similar to the Federal Test Procedure FTP-75 used by EPA-USA, following the EPA urban driving cycle. Fuel economy measurements were also obtained using volumetric meters for more accuracy. HC (ppm) and CO (ppm) emissions at idle were also measured before each test. The carburetors were evaluated following the CRC Carburetor Deposit Rating Technique included in the CRC Carburetor and Induction System Rating Manual (CRC Manual 16) at 0 kilometers and at 10000 kilometers of each phase. All the data generated during the field test was statistically treated using linear regression models to calculate mean differences for the variables studied. Least significant differences were calculated for each variable in each phase using Tukey's Test Criterion at the 95 % confidence level. These analyses showed that both additives reduced the deposit level on the carburetors of one of the evaluated car models and had no significant effect on the other. There were no significant effects on fuel economy for both additives evaluated. There was a decrease of HC emissions at idle for the two vehicle models using both additives, and there were no other relevant effects on any of the other emissions measured. From these findings, it can be concluded that the additives evaluated did not effectively clean the carburetors critical areas (air bleed, venturi, etc). This is supported by the fact that even though both additives showed a significant effect on cleaning the throttle body area (CRC technique) on one of the car models, that cleanliness did not translate into benefits in fuel economy or emissions.