The importance of the fuel in providing improved vehicle performance and reduced emissions has become widely recognized, especially in the past ten years. In 1998, an SAE paper was presented providing a systematic analyses of 1996 United States gasoline quality. This paper extends the methodology of that paper to include the impact of fuel composition on evaporative emissions, and it provides analyses of gasoline quality for the years of 1996, 1997 and 1998.The vehicle performance and emissions characteristics of gasolines were determined using data from surveys of United States' service station gasoline samples. Results are presented for: gasoline type (California RFG - reformulated gasoline, Federal RFG, low RVP - Reid Vapor Pressure, and conventional); gasoline grade (regular, intermediate and premium); individual cities; individual brands (coded); and for sulfur content. It is concluded that: differences exist among commercial gasolines for all of the items evaluated; the differences are narrowing; and overall gasoline quality is improving.