Five Methods to Determine if Engine Oil Has Gone Bad

Engine oil holds an extremely crucial position within a vehicle. Its quality has a direct and significant impact on the performance of the engine. Thus, it is essential for us to master certain methods for identifying the condition of engine oil to provide better protection for the engine. Today, let’s have Master Zhang, a truck-mounted crane driver with numerous years of driving experience, share some effective ways to identify deteriorated engine oil.

The lighting method: On a sunny day, utilize a screwdriver to lift the lubricating oil at a 45-degree angle in relation to the horizontal plane and closely observe the oil droplets. Under the illumination of light, if there are no abrasive debris present within the lubricating oil, it indicates that the oil is in good condition and can be used without concerns. However, if an excessive amount of abrasive debris is detected, it is a clear indication that the lubricating oil should be replaced promptly.

High-quality engine oil typically exhibits a semi-transparent yellow-brown hue. In cases where water is present in the engine oil, it will assume a brown color. After the engine has been operational for a certain period, the engine oil might turn milky white and be accompanied by foam. Black engine oil usually suggests an excessive accumulation of sludge, iron filings, or an abundance of carbon particles. When you pull out the oil dipstick and observe it against the light, if the graduation line cannot be clearly discerned through the engine oil on the dipstick, it implies that the engine oil is overly dirty and requires immediate replacement.

The abovementioned approach constitutes the visual inspection method. Additionally, there exists another method involving the use of test strips, specifically slow qualitative test strips. These strips are primarily employed for the determination of ions and chemical components. They have the capability to ascertain whether a sample contains a specific quantity of a particular substance. The test strips designed for engine oil detection can determine the conditions of various components contained within the engine oil, thereby enabling the assessment of whether the engine oil has aged.

The test procedure is as follows: Remove the dipstick, deposit a single drop of engine oil from the dipstick onto the slow qualitative test strip, and then position the test strip horizontally. Wait for a duration of 24 hours. It will be observed that after 24 hours of standing, the following three significant ring areas will manifest on the test strip.

The sediment ring: Positioned at the center of the spot, this is where the coarse particle impurities within the oil accumulate. The depth of the color of the sediment ring can provide a rough estimation of the degree of oil contamination.

The diffusion ring: The ring band situated outside the sediment is referred to as the diffusion ring. It represents the trace left behind by the outward diffusion of fine particle impurities suspended within the oil. The finer the particles, the greater the distance they diffuse. The width and color uniformity of the diffusion ring are crucial factors, as they indicate the dispersion capacity of the additives present in the oil for contaminated impurities.

The oil ring: Positioned outside the diffusion ring, the color of the oil ring ranges from light yellow to brownish red, signifying the oxidation degree of the oil.

The color of the engine oil that has diffused on the test strip enables the differentiation of the engine oil quality into four grades:

Grade 1: When there is no distinct boundary between the sedimentation area and the diffusion area of the oil spot, and the entire oil spot displays a uniform color with a light and bright oil ring, it indicates good oil quality.

Grade 2: If the sediment ring appears dark, the diffusion ring is wide, and there is a clear dividing line, and the oil ring exhibits different depths of yellow, it suggests that the oil quality is contaminated. Nevertheless, the engine oil can still be utilized.

Grade 3: A dark black sediment ring, dense sediment, a narrow diffusion ring, and a deepening color of the oil ring indicate that the oil quality has deteriorated.

Grade 4: When only the central sediment ring and the oil ring are present, with the absence of a diffusion ring, a black sediment ring with dense and thick sediment that is not prone to drying, and a deep yellow and light brown oil ring, it implies that the oil quality has oxidized and deteriorated.

Slowly pour the engine oil from the measuring cup into another empty cup and attentively observe its flow pattern. Good-quality engine oil should flow in a slender, uniform, and continuous manner. In contrast, deteriorated engine oil will present in the form of oil droplets.

Let’s elaborate on this aspect. The flow characteristics of engine oil can provide valuable insights into its condition. A smooth and continuous flow indicates that the viscosity and consistency of the oil are within the optimal range, allowing it to lubricate the engine components effectively. On the other hand, if the oil trickles down in droplets or shows an uneven and interrupted flow, it may suggest that the oil has thickened or lost its lubricating properties, potentially indicating deterioration.

Pour the engine oil between the thumb and the index finger and gently rub it. The sensation should be one of lubrication, free from abrasive debris or friction. If a significant friction feeling similar to that of sand grains is perceived between the fingers, it is an indication that there are iron filings, sludge, and impurities present within the engine oil.

This tactile assessment is a direct way to sense the presence of contaminants or abnormal particles in the oil. A smooth and consistent feel indicates that the oil is relatively clean and in good condition. However, the presence of gritty or rough textures can signify that the oil has accumulated debris over time, which may compromise its performance and protective capabilities.

On a sunny day, select a location with ample and good light. Use an engine oil inspection stick or dipstick to lift the engine oil and then observe the oil droplets against the sunlight. Under the light, if there are no abrasive debris visible within the engine oil, it suggests that the oil can be used continuously. Conversely, if an excessive amount of abrasive debris is observed, it indicates that the engine oil has deteriorated and is no longer suitable for use.

The transparency of the engine oil is a visual cue of its purity. Clear and debris-free oil ensures that it can flow freely through the engine’s intricate components, providing effective lubrication and protection. Any visible particles or cloudiness can be a sign of contamination or breakdown of the oil’s composition.

All engine oil with a strong and unpleasant smell that stimulates the sense of smell is either deteriorated or of inferior quality. Good engine oil should have no distinct or overpowering smell, perhaps only a faint and pleasant fragrance.

A pungent or abnormal odor can suggest chemical changes or degradation within the engine oil. Fresh and properly functioning engine oil typically has a relatively neutral or minimally detectable scent. A pronounced and unpleasant smell is often an indication that the oil has undergone undesirable alterations and may no longer be providing the necessary protection for the engine.

If the deteriorated engine oil is not replaced in a timely manner, it will cause significant damage to the engine, adversely affect its service life, and may even lead to other serious safety incidents. Hence, it is imperative for everyone to frequently inspect the engine oil condition of their cherished vehicles.

Regular checks and prompt replacement of deteriorated engine oil are not only essential for maintaining the optimal performance of the vehicle but also contribute to extending the engine’s lifespan and ensuring safe driving. By being vigilant and proactive in monitoring the engine oil, vehicle owners can safeguard their investment and minimize the potential for costly repairs and breakdowns.