This paper describes Nissan's research and development work on flexible fuel vehicles. Nissan has been engaged in R&D activities for flexible fuel vehicles to examine the possibilities for long-range energy conservation and air quality improvements. The flexible fuel research vehicle described here employs an electrostatic type sensor to measure the methanol concentration in the fuel and the engine system has been designed to burn a wide variety of fuels from M85 to MO (gasoline). Test results obtained with this research vehicle indicate that OMHCE and NOx emissions with M85 are lower than with MO under a fresh catalyst condition. However, by the end of a 50,000 mile durability test, NOx emissions with M85 increase to the same level as with MO. The use of M85 as the fuel results in a pronounced increase in aldehyde emissions compared with MO.