What must be done after a cold start until oil pressure returns to normal range?

Remaining at idle after a cold start until oil pressure returns to normal range is critical for several reasons. Primarily, at engine start, the oil is cold and highly viscous, which can impede the flow of oil to the engine components. By keeping the engine at idle, you allow the oil to warm up gradually, which helps reduce its viscosity and ensures it circulates properly through the engine.

This practice is essential for protecting the engine from wear and tear that can occur when cold oil fails to lubricate vital engine parts effectively. During this period, the engine can reach optimal operating temperature and pressure, minimizing the risk of damage caused by inadequate lubrication.

Other options might suggest actions that increase engine load or RPM prematurely, which can lead to increased wear or damage while the engine is not adequately lubricated. Therefore, the best and safest course of action is to remain at idle, allowing for an appropriate warm-up period.