Which of the following can cause low engine oil pressure?

Low engine oil pressure is commonly linked to issues with the oil itself, such as its quantity or the mechanism responsible for circulating it. When oil levels are low, there is insufficient lubrication available for the engine components, which can lead to inadequate pressure being built up throughout the engine's lubrication system. Additionally, a defective oil pump may fail to circulate oil efficiently or may not be able to maintain the necessary pressure due to wear or internal failure. Without proper oil pressure, the engine can suffer from increased friction, overheating, and, ultimately, significant damage.

Other options, while they may impact engine performance in various ways, do not directly relate to oil pressure. High fuel levels, for example, might lead to other issues like flooding the engine or causing poor combustion, but they wouldn't directly affect oil pressure. Similarly, a clogged air filter could restrict air flow to the engine and impact performance but is not related to the oil circulating within the engine. Worn spark plugs could lead to engine misfires or poor ignition but have no bearing on oil pressure. Therefore, low oil levels or a defective oil pump is the primary cause of low engine oil pressure.