If the oil pressure gauge fluctuates over a wide range from zero to normal operating pressure, the most likely cause is

If the oil pressure gauge fluctuates over a wide range from zero to normal operating pressure, the most likely cause is

• A. Air in lines
• B. Sudden temperature change
• C. Oil viscosity too high
• D. Low oil supply

Answer: (D)

Oil pressure stays up when the pump can deliver a steady volume of oil to the bearings. If the gauge swings from near zero to normal, the pump is intermittently starving for oil rather than suffering a change in oil properties or a leak somewhere. The most likely cause is low oil supply—oil level is too low or the pickup is not consistently submerged (or it's being starved by a restriction), so the pump occasionally draws air or gas and the pressure collapses, then recovers once oil is drawn in again. In other words, when there isn’t enough oil available for the pump to maintain pressure, you’ll see those wide fluctuations as the system alternates between starvation and normal operation. Check the oil level, inspect the pickup screen for blockage, and look for any restrictors or leaks in the supply path to restore a steady pressure.

Oil pressure stays up when the pump can deliver a steady volume of oil to the bearings. If the gauge swings from near zero to normal, the pump is intermittently starving for oil rather than suffering a change in oil properties or a leak somewhere. The most likely cause is low oil supply—oil level is too low or the pickup is not consistently submerged (or it's being starved by a restriction), so the pump occasionally draws air or gas and the pressure collapses, then recovers once oil is drawn in again.

In other words, when there isn’t enough oil available for the pump to maintain pressure, you’ll see those wide fluctuations as the system alternates between starvation and normal operation. Check the oil level, inspect the pickup screen for blockage, and look for any restrictors or leaks in the supply path to restore a steady pressure.