Why must air tanks be drained before driving?

Draining air tanks before driving is crucial primarily to remove water and compressor oil that can accumulate in the air system. Over time, moisture can condense in the air tanks, especially in colder temperatures. If this moisture is not removed, it can freeze. The ice can obstruct the air lines and components, leading to potential brake failure. Proper brake function is essential for vehicle safety, so ensuring that the air tanks are free of contaminants like water and oil is vital for maintaining the integrity of the braking system.

While adjusting pressure for better fuel economy, improving air conditioning effectiveness, and ensuring air supply for horns might seem important, they are not the primary reasons for draining air tanks prior to driving. The focus on moisture removal directly addresses the safety concerns associated with frozen water obstructing braking functionality.