What should the oil pressure gauge indicate after starting the engine?

The oil pressure gauge should indicate increasing or normal oil pressure after starting the engine because this indicates that the oil pump is circulating oil throughout the engine and lubricating its internal components. Adequate oil pressure is crucial for the functioning and longevity of the engine, as it ensures that oil reaches critical areas to reduce friction and wear.

When the engine starts, oil is pumped from the oil pan through the oil filter and into the engine. Initially, the oil pressure may rise quickly as the lubricant fills the engine's internal passages. A reading of increasing or normal pressure demonstrates that the oil system is functioning correctly and that there are no leaks or obstructions.

As for the other choices, if the oil pressure gauge shows no change in pressure, that could indicate a problem with the oil pump or a sensor failure. Fluctuating pressure may suggest issues such as low oil level or a failing oil pump, which can be harmful to the engine. Additionally, if the warning light remains on, it signals a critical issue that requires immediate attention, such as low oil levels or insufficient oil pressure, which can lead to severe engine damage. Therefore, a reading of increasing or normal oil pressure is the desirable and correct outcome.