Which of the following is a sign of fuel contamination?

The presence of water at the bottom of the tank is indeed a sign of fuel contamination. Water can enter fuel storage tanks through various means, such as condensation, leaks from above-ground or underground sources, or rainwater intrusion. When water mixes with fuel, it can lead to a plethora of problems including microbial growth, which can create sludge that clogs filters and affects the performance of engines. Additionally, water in fuel can cause rust and corrosion in tanks and pipes, further compromising the quality of the fuel.

In contrast, clear and bright color typically indicates that the fuel is clean and free from contamination. A stable temperature might suggest that the fuel has not been subjected to extreme environmental conditions that could lead to contamination. Similarly, a consistent smell is often associated with pure fuel, reaffirming its quality. Recognizing these signs can help fuel handlers maintain fuel integrity and prevent operational issues.