How to Determine if Engine Oil Needs Replacement?

[MadelineLee]

Methods to determine if engine oil needs replacement: 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 old oil between your thumb and index finger repeatedly. Good-quality oil will feel smooth, with few particles and no friction. If you feel impurities, poor viscosity, or even a gritty sensation, it should be replaced. 3. Color Test: Place a few drops of old oil on a clean white filter paper. After the oil spreads, high-quality oil will leave no powder, feel dry and smooth to the touch, and show a clear yellow diffusion ring. If the oil appears dark brown with impurities, it should be replaced. 4. Light Test: Hold the dipstick at a 45-degree angle under light to observe the oil droplets. If you can clearly see no particles in the droplets, the oil is still good. If there are many particles, it should be replaced.

[DelJoshua]

I've been driving for twenty years, and when it comes to changing oil, experience and intuition are the most reliable. Pull out the dipstick and check—if the color resembles dark coffee, it's time for a change. If it's as black as soy sauce, don't delay any longer. Dip your fingertip in the oil and rub it; if it feels rough or has a gritty texture, those are signs of aging. Fresh oil has good stringing effect—if it doesn't cling and just drips off, it's definitely overdue for a change. Also, be alert if the engine noise increases or there's a lack of power while driving, as these could indicate insufficient lubrication. I recommend checking every seven to eight thousand kilometers, and don't put too much faith in those official claims of fifteen thousand kilometers.

[McCarlos]

I rely heavily on the vehicle's own signals. The maintenance reminder light is the most straightforward—when the yellow oil can icon lights up, it's time for a change. Modern cars also have oil monitoring systems; if the dashboard shows engine oil life below 20%, it's time to act. Difficulty during cold starts can also be a sign, especially when the engine struggles noticeably in cold weather, which may indicate degraded oil viscosity. Always check the oil before long trips—I've encountered situations where the dipstick showed levels below the 'min' line. Don't wait for an alarm to take action; if the oil pump fails, it might be too late.

[MacAnthony]

Checking engine oil condition requires expertise. Use a test strip to observe the oil's diffusion ring - a wider sediment ring indicates dirtier oil, while blurred oil ring boundaries signal aging. For a professional approach, measure viscosity: new oil should have a viscosity around 13 at 100°C; if it drops below 9, replacement is mandatory. Oil with over 0.2% water content will emulsify - check the dipstick against light for milky appearance indicating water contamination. It's best to keep a testing pen handy; replace immediately if the base number (TBN) falls below 2. When changing oil yourself, inspect metal shavings in the old filter - excessive amounts indicate engine wear.