How to Identify if Engine Oil Has Deteriorated?
2 Answers
Here are the criteria for identifying whether engine oil has deteriorated: 1. Observe the fluidity of the engine oil. 2. Smell the engine oil for any unusual odors. 3. Feel the texture of the engine oil by hand. 4. Use qualitative filter paper to determine. Here is relevant information about deteriorated engine oil: 1. When touching normal engine oil, it feels smooth and free of debris; deteriorated oil may contain metal shavings or impurities, making it feel rough and increasing friction. 2. If the engine oil has a pungent smell or a noticeable sour or foul odor, it can be determined as deteriorated oil. 3. Normal engine oil does not have a strong, irritating smell; it only has a mild, pleasant aroma.
The most direct way to check if engine oil has deteriorated is by observing its color and condition. I prefer checking the oil dipstick when the engine is cold—first wiping it clean with a tissue, then reinserting and pulling it out to inspect. Fresh oil is translucent amber or light brown in color. It's normal for the color to darken after a few thousand kilometers, but if it turns as black as soy sauce with a slightly gritty texture, it’s likely severely oxidized or has excessive carbon buildup. Smell is also crucial; fresh oil has only a faint mineral oil scent. If it smells sour or burnt, it’s definitely deteriorated. Additionally, rubbing the oil between your fingers helps—normal oil has high lubricity, while deteriorated oil may feel gritty or sticky. A milky appearance indicates water contamination and emulsification, requiring immediate replacement. Don’t forget to consider the maintenance interval—full synthetic oil typically needs inspection after 8,000 to 10,000 kilometers.
