Several tests, simulating the urban utilization of a diesel engine, were conducted in an chassis dynamometer to acknowledge the indirect injection engine performance and emissions when using several percentages of biodiesel, from lean diesel (B0) to 100% biodiesel (B100),. After these preliminary tests, some blends of this soybean based fuel were rejected. The remaining fuels were tested more accurately, following the prescriptions of the regulation, with some extra-urban test conditions. The purpose is to know the differences regarding consumption and emissions results. Considering these results, the goal is to evaluate what the most efficient fuel for this kind of engine is, crossing the performance tests results with the extra urban tests results. The base perspective is that there’s no need to study neat biodiesel. The only reason why the use of this particular fuel is tested is to have the perception of the end of the scale results. Reinforcing this idea, the worst data was obtained using B100. Thinking globally, there’s no way to get enough vegetable oil to replace completely the diesel use, without causing ambient and social irreparable damages. The specific fuel consumption results were somewhat surprising, giving hope to the biodiesel use. One must consider the fact that these tests were made on engines that have been developed to get a bigger efficiency out of diesel and not biodiesel. There is still a long way to go in order to achieve this kind of performance using biodiesel blends. The goal of this project is to get a deeper knowledge on the origins of the differences and work on that to achieve better engine performance when using some biodiesel blends