Currently, a majority of the ‘gasoline’ sold at the pumps in the United States is a nominal blend of 90% gasoline and 10% ethanol. This mixture is commonly referred to as E10. This paper reports on a study conducted to determine the effects of E10 on the fuel system performance of vintage automobiles. The study focused on the potential degradation in performance of the carburetors and fuel pumps due to exposure to E10. Six fuel systems were selected for study including the 1948 Flathead Ford, 1958 Volkswagen Beetle, 1962 Ford Falcon, 1969 Chevrolet Bel Air and 1970 Chrysler New Yorker. The components tested were either rebuilt original equipment or new aftermarket replacement parts, depending on availability. Although the components tested were not all original equipment parts, they represent a reasonable sample of the types of parts likely to be found in vintage vehicles currently on the road.The fuel system components were tested under both dynamic and static conditions. The dynamic tests were designed to study the operational performance of the components. For dynamic testing, two sets of components were acquired for each model fuel system. The components were assembled in test rigs that mimicked their operation in a vehicle. One set was tested using straight pump-grade gasoline (E0) and the other set was tested using pump-grade E10. The systems were operated for 1600 to 2400 hours at a 25 percent duty cycle. In addition to the run hours, the fuel systems were allowed to sit idle and exposed to fuel for an additional 2600 hours between run cycles, for a total exposure time of 4200 hours. Periodically the fuel pump flow rates and pressure heads were measured. All systems were found to be performing normally throughout the test period. After completion of the testing each component was disassembled and examined for signs of material damage. The most common observation was staining and tarnishing. Nothing was found that would suggest the imminent failure of a part.The static exposure tests were designed to identify material damage caused by alternately wetting and drying the components. These tests were conducted on a third set of components which were cut into sections and periodically sprayed with either E0 or E10. The periodic exposure, a 5 minute soaked followed by a 55 minute dry time exposure in air, was intended to accelerate potential swelling/shrinking problems with seals/gaskets and corrosion problems on metals. After 3000 hours of exposure minor changes were noted, but nothing that would suggest imminent failure of a part.