Some chemical characteristics and natural impurities of diesel fuel used in diesel engines may damage the operation of emission control devices as well as contribute to the formation of secondary pollutants in the atmosphere. Sulfur is one of the natural impurities of diesel fuel, which upon burning, combines with oxygen to form SO2, creating emissions that adversely affect both the environment and human health. Many countries around the world have adopted stringent diesel emission standards to drastically reduce the sulfur content in diesel fuel and thereby improve air quality. Many authors have addressed the need to regulate transportation fuel emissions from pollutants, including sulfur (S), carbon monoxide (CO), particulate matter (PM), nitrogen oxides (NOx) and hydrocarbons (HC). This paper addresses both regulated and non-regulated emissions from four types of diesel fuels, each with a different sulfur concentration. The following four types of fuels were tested in a diesel passenger car over a chassis dynamometer according to FTP 75 cycle: a) Ultra Low Sulfur Diesel S10; b) Very Low Sulfur Diesel S50, c) Low Sulfur Diesel S500, and d) High Sulfur Diesel S1800. A set of at least three tests were performed with each type of fuel. Regulated emissions of pollutants, such as HC, CO, NOx, and PM, were measured by Horiba 7000 series benches. Non-regulated emissions were analyzed for constituents, such as formaldehyde, acetaldehyde and sulfur dioxide. Specialized Fourier Transform Infra-red Spectroscopy (FTIR - AVL/SESAM) was used to generate the data for this work. Based on the data collected, a comparative study of different fuels was conducted.