Oil and water typically collect in which component of heavy vehicle air systems?

• A. Fuel and coolant
• B. Ice and snow
• C. Oil and water
• D. Sand and dirt

Answer: (C)

In the air brake system, moisture and oil from the compressor tend to collect in the air tanks, which act as the storage reservoir for compressed air. As the air is cooled in the tanks, water condenses out, and oil carried by the compressor can mix with that condensate, accumulating in the tanks. Regular draining of these tanks is essential to remove this buildup and prevent corrosion, freezing, or brake performance issues. The other options don’t fit because fuel and coolant are part of the engine and cooling/fuel systems, not the air system; ice and snow aren’t the intended collection point in these components; and sand and dirt are contaminants that should be filtered out, not stored in the tanks.