When evaluating a used fuel tanker, the most critical technical aspect is the tank integrity and material thickness. You must verify if the tank is made of carbon steel, stainless steel, or aluminum alloy, as this determines the types of fuel it can carry and its lifespan. Check the tank shell for any signs of welding repairs, patches, or corrosion. Additionally, inspect the suspension system (mechanical or air suspension) and the axle brand (e.g., BPW or FUWA) to ensure they can handle the rated load capacity, typically ranging from 30,000 to 50,000 liters.