How to Determine Whether to Change Car Engine Oil?

[EvelynMarie]

Methods to determine whether car engine oil needs to be changed are as follows: 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. Finger Rub Test. Rub the extracted old oil repeatedly between your thumb and forefinger. Good quality oil will feel lubricated, produce little residue, and feel frictionless. If you feel impurities, poor viscosity, or even a gritty sensation, it should be changed. 3. Color Identification Test. Place a few drops of old oil on a clean white filter paper. After the oil seeps through, good quality oil will leave no powder, feel dry and smooth to the touch, and show a clear yellow infiltration zone. If it appears dark brown with impurities, it should be changed. 4. Light Inspection Test. Hold the dipstick at a 45-degree angle and observe the oil drops under light. Good oil will clearly show no residue particles in the drops. If there are many particles, it should be changed.