Which is not a likely cause of low system air pressure?

The presence of compressor oil in cylinders usually does not contribute to low system air pressure. In fact, compressor oil is intended to lubricate the moving parts within the compressor, which can help maintain efficiency and prevent wear. While excess oil can create issues such as reduced airflow or higher maintenance needs, it is not generally a direct cause of low air pressure in a pneumatic system.

On the other hand, pipe rust and scale particles can obstruct airflow by clogging pipes or filters, which could lead to lower pressure readings. Side load mounting forces can misalign components, leading to inefficiencies or leaks that affect system pressure. Similarly, worn seals due to insufficient lubrication can cause air leaks, significantly reducing the system's pressure. These factors are likely to contribute to reduced air pressure, making them critical considerations for maintaining system performance.