Two different types of fuel sources, namely conventional diesel and GTL diesel, were used to conduct a study of their effects on engine emissions and performance. Varying loads were applied to obtain concise data when contrasting the aforementioned fuels. Key parameters such as net power output, torque, engine speed and efficiency were measured. The engine and the dynamometer were operated via an automated closed-loop control system. On-road study found that the volumetric fuel consumption of GTL diesel was higher by up to 3.3% when compared to conventional diesel; there were drastic reductions in the levels of regulated emissions when using GTL by 36% for CO, 4.2% for CO2, 47% for THC (total hydrocarbons) and 35% for NOx, compared to conventional diesel.