What is a likely cause of fluctuating oil pressure from zero to normal operating pressure?

Fluctuating oil pressure from zero to normal operating pressure is commonly associated with an insufficient oil supply. When the oil level is low, the oil pump may not be able to effectively draw oil, leading to pressure fluctuations. This can occur due to leaks, consumption, or inadequate oil maintenance, all of which may result in the oil system not retaining the necessary fluid levels to maintain steady pressure.

In contrast, a broken or weak pressure relief valve spring would typically cause a constant pressure that is either too high or not adjustable, rather than fluctuations from zero to normal pressure. An air lock in the scavenge pump intake might prevent proper oil return and could create more consistent low pressure rather than fluctuations. Finally, if the oil viscosity is too low, it would likely lead to a consistently low pressure rather than fluctuations, particularly during varying engine load or operating conditions. Thus, the context of these choices helps clarify why a low oil supply is associated with oil pressure fluctuations.