What is the correct method to measure engine oil?

[AshlynAnn]

Here is the correct way to check engine oil: 1. Smell test. Pull out the dipstick and smell it closely. If there is a strong sour odor, it indicates the oil has deteriorated and should be changed. 2. Rubbing method. Rub the extracted old oil repeatedly between your thumb and forefinger. Good-quality oil will feel lubricated, produce little residue, and have no friction. If you feel impurities, poor viscosity, or even a gritty sensation, it should be changed. 3. Color test. Take a clean white filter paper (or a good-quality tissue), drip a few drops of old oil on it, and observe the color after the oil has seeped through. Good-quality oil will have no powder, feel dry and smooth to the touch, and show a clear yellow infiltration zone. If it appears dark brown or has impurities, it should be changed. 4. Light test. Hold the dipstick at a 45-degree angle under light and observe the oil droplets. If you can clearly see no residue in the droplets, the oil is still good. If there is a lot of residue, it should be changed.