The study analyzed the performance of a diesel engine using Pertamina dex fuel by looking at energy and exergy. The researchers wanted to see how efficient the engine was in generating power. They tested the engine at different torque levels to find the optimal operating conditions. The results showed that the engine was most efficient at 1991 rpm with 9 Nm torque, reaching an efficiency of 22.89%. At 2484 rpm with 1 Nm torque, the engine had the highest exergy destruction.