Adulteration of petrol and diesel fuel with kerosene is very common in Tanzania. It increases the tailpipe emissions of harmful pollutants from vehicles. These leads to this study, which tends to show the rate of emission of CO (carbon II oxide) and PM (Particulate matters) from engines when they are run on adulterated fuel. Petroleum products are essential inputs needed in economic activities, hence a necessity for the economy of any Country. Adulteration of petroleum products especially petrol (motor gasoline) and diesel (high speed diesel (HSD)), has become a serious problem. Expensive consumer products are often adulterated by integrating with cheaper low quality materials having similar physical and chemical properties. Kerosene is the most important domestic fuel for economically weaker sections of society and hence is heavily subsidized. The large differences in the prices of petrol, diesel and kerosene, the easy availability of kerosene and the fact that it is miscible in petrol and diesel, make the unhealthy and unethical practice of adulteration of petrol and diesel a very plausible proposition. Effects of adulteration on the environment and on human health were discussed and possible solutions to combat adulteration of fuel were highlighted.