The oil inspection should be carried out in a cold state:

1. In the hot car state, after the engine is started, the oil expands due to overheating, and the measurement of the oil dipstick will not be accurate. In addition, when the car is hot, the engine oil will fall onto the cylinder head and will not immediately flow to the oil pan;

2. The function of the oil dipstick is to measure the height of the static oil level, thereby reflecting whether the engine oil inventory is within a reasonable range. Conventional oil dipsticks have clear upper and lower limits, as long as the detected oil level is between the upper and lower limits. It would be best if it could be in the middle position;

3. It should be noted that more engine oil is not necessarily better. The higher the oil level, the greater the resistance of the engine (because the crankshaft needs to constantly stir the oil pan to achieve splash lubrication). Ideally, the liquid level can be kept slightly lower in the middle position, which minimizes the resistance and fuel consumption of the engine, while maintaining stable lubrication performance.