What are the diagnostic methods for engine oil deterioration?

[MacCharlotte]

Diagnostic methods for engine oil deterioration are: 1. Smell test: Open the front compartment cover, pull out the dipstick, and bring it close to your nose to smell. If there is a strong sour odor, it indicates the oil has deteriorated and needs immediate replacement. 2. Finger rub test: Use the dipstick to extract a small amount of oil and rub it repeatedly between your thumb and forefinger. If you feel impurities, poor viscosity, or even a gritty sensation, the oil is in a deteriorated state and should be replaced promptly. The functions of engine oil are: 1. To reduce friction and high temperatures; 2. To minimize gas leakage and prevent contamination from external pollutants; 3. To prevent contact between water, air, acidic harmful gases, and engine components; 4. To cushion the pressure rise in the engine cylinder ports; 5. To clean away dirt generated on the working surfaces of components.

[VanJocelyn]

I diagnose oil degradation mainly through several common methods that can be easily done at home, which are very simple and practical. First, pull out the dipstick to check the color and texture. Normal engine oil is golden yellow or amber in color; if it turns dark black or cloudy, it may indicate degradation. Then, smell the oil—fresh oil has little to no odor, but degraded oil will have a burnt or sour stench, which is quite pungent. Next, test the viscosity: drop a bit on clean paper or rub it between your fingers. Good oil has high viscosity and feels smooth, while oil that’s too thin like water suggests severe aging. I’ve also noticed that increased engine noise or abnormal fuel consumption can signal oil issues. Oil degradation is usually caused by infrequent changes, high-temperature environments, or contamination with dust and moisture. If not addressed promptly, it can lead to engine wear and damage. I recommend checking the oil condition every 3,000 to 5,000 kilometers as part of regular maintenance—developing this habit can help avoid major repair troubles.

[VanElle]

Diagnosing Engine Oil Degradation I have my own habits, especially in daily car use. The first step is to pull out the dipstick and observe: good oil is clear and transparent, while degraded oil turns black or has suspended particles, as if tiny impurities are mixed in. Next, I usually smell it; fresh oil has a mild odor, but once degraded, it smells like burnt oil, very pungent. Viscosity testing is also important: drop a bit on your hand and rub it, if it doesn't feel slippery enough or spreads too quickly, it indicates reduced viscosity and aging. I also consider the mileage; if it exceeds the manufacturer's recommended service interval (e.g., 10,000 kilometers), the oil is more likely to degrade. Causes of degradation include prolonged high temperatures, contamination, or oxidation, and not changing the oil in time may lead to reduced engine efficiency or unusual noises. For prevention, I conduct a comprehensive oil check every six months, using simple tools for testing.

[HannahMarie]

I diagnose engine oil degradation mainly by three simple signals: visual, olfactory, and tactile. Open the hood, pull out the dipstick, and check the color: if it's darkened to deep black or shows milky emulsification, it's dangerous. Smell the oil—degraded oil has a burnt or sour odor. Rub the oil between your fingers to test viscosity; if it's too thin, that's not good. Additionally, pay attention to engine noise becoming louder or difficulty starting, which could also indicate oil issues. Degradation is usually caused by contamination or aging, so timely oil change is crucial.