When should the engine oil level be checked?

Checking the engine oil level while the engine is shut down is the correct practice because it ensures an accurate reading. When the engine is running, oil is circulated throughout the engine, which can lead to mismeasurement as oil is not settled in the oil pan. Similarly, checking the oil immediately after a short drive may also yield an inaccurate result, as the oil may not have had enough time to drain back into the oil pan. It's important to allow the engine to sit for a few minutes after being shut off, allowing the oil to settle.

During warm-up, the engine is still running and oil is being circulated, which is not ideal for checking levels. Therefore, verifying the oil level with the engine in a shut down state is the best approach to ensure that the measurement reflects the actual amount of oil in the system.