How to Choose and Maintain Engine Oil: A Guide for Auto Dealers and Parts Buyers

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How to Choose and Maintain Engine Oil: A Guide for Auto Dealers and Parts Buyers

Feb 5th ,2024

Engine oil, also known as engine lubricant, with its English name being "Engine Oil," has a density of approximately 0.91×10³ kg/m³. It plays a pivotal role in lubricating and reducing friction, assisting in cooling and temperature reduction, sealing to prevent leaks, protecting against rust and corrosion, and providing damping and cushioning effects. It is often referred to as the "blood" of a car.

Engine oil consists of two main components: base oil and additives. The base oil is the primary component of the lubricant, determining its basic properties. Additives are used to compensate for and improve the performance aspects where the base oil may be lacking, imparting new properties and forming a crucial part of the lubricant.

The engine, the heart of the car, contains many metal surfaces that move against each other. These components operate at high speeds, under poor conditions, with working temperatures reaching between 400°C and 600°C. Under such severe conditions, only quality lubricants can minimize wear on engine parts and extend their lifespan.

Market-available engine oils can be broadly categorized into mineral oils and synthetic oils (excluding vegetable oils due to their scarce production). Synthetic oils are further divided into fully synthetic and semi-synthetic.

Lubricant base oils are mainly divided into mineral base oils and synthetic base oils. Mineral base oils are widely used, making up over 95% of usage, but synthetic base oils are necessary for certain applications.

How are automotive oil grades classified? When purchasing engine oil, selecting the correct oil grade is a crucial factor. How do you choose the right oil product for your beloved car? First, it's essential to understand the method of classifying automotive oil grades. Essentially, the oil's grade represents its viscosity. Different grades indicate different viscosities.

This viscosity is primarily classified according to the SAE (Society of Automotive Engineers) standards.

For passenger cars, multi-grade oils are commonly used, marked as AW-B, where A and B are numerical values. "W" stands for winter, indicating that the lower the number before W, the lower the oil's viscosity at low temperatures, hence better flowability and suitability for lower minimum temperatures. Commonly seen grades include 0W and 5W.

0W oil offers better flowability at low temperatures compared to 5W.

According to the SAE grading standards, 0W oil can ensure normal startup at -35℃, while 5W oil is designed for -30℃.

In essence, the lowest usage temperature of the oil can be determined by adding -35℃ to the number before W. If local winter temperatures can drop below -30℃, it is advisable to opt for 0W oil. Next, regarding the number after W, it signifies the oil's "high-temperature performance."

This typically refers to the oil's viscosity range at the optimal working temperature (100℃). The higher the number, the greater the oil viscosity at high temperatures, the poorer the flowability, but the more stable the oil film, which can prevent engine wear. To know which grade of oil you need, the most convenient way is to consult your vehicle's maintenance manual and purchase accordingly.

Beware of Inferior Counterfeit Engine Oil

Moreover, when buying engine oil, besides checking the grade, it is crucial to avoid purchasing inferior or counterfeit engine oil.

Distinguishing Real from Fake First, examine the packaging appearance. Brand-name oils have a one-time cap with a sealed tin foil at the notch, bearing the manufacturer's special mark. The absence of these features could indicate counterfeit oil.

Additionally, to prevent counterfeiting, brand-name oils have special markings in inconspicuous places such as the label sticker, the bottom of the can, inside the cap, and on the handle. If counterfeiters customize packaging, comparing the real and fake packaging can reveal discrepancies.

Second, observe the oil quality. Genuine oil is light and transparent, free from impurities, suspended particles, or sediment, and flows well when shaken. Counterfeit oils may be darker, contain impurities or sediment, have a strong, irritating odor, show poor flowability when shaken, or leave streaks when touched.

Counterfeit oil products generally fall into three categories:

Recycled waste oil that is processed and bottled for sale.

Pure base oil mixed without any additives.

Low-grade oil bottled and sold as higher quality. Counterfeiters usually adjust the color of fake lubricant to match that of genuine oil.

Common Misconceptions 

Misconception 1: Change the oil when it turns black This understanding is not comprehensive. For lubricants without quieting dispersants, blackening indeed indicates the oil has severely degraded. However, modern automotive lubricants generally contain quieting dispersants. These agents clean the adhesive film and black carbon deposits from the piston, dispersing them in the oil, reducing the formation of high-temperature deposits. Thus, the oil turning black after some time does not necessarily mean it has completely degraded.

Misconception 2: More oil is always better The oil level should be maintained between the upper and lower marks on the dipstick. Excess oil can enter the combustion chamber from the gap between the cylinder and piston, forming carbon deposits. These deposits can increase engine compression ratio, leading to detonation; red-hot carbon deposits can cause pre-ignition, exacerbating wear on cylinders and pistons, and accelerating lubricant contamination. Additionally, excess oil increases the resistance against the crankshaft connecting rods, leading to higher fuel consumption.

Misconception 3: Additives are highly beneficial High-quality lubricants already contain a variety of engine-protecting additives, including anti-wear agents, and are balanced to ensure full performance. Adding other additives not only fails to provide extra protection but may react with chemicals in the oil, decreasing overall performance.

Misconception 4: Topping up oil without changing it is sufficient While regularly checking oil levels is correct, merely topping up without changing can only compensate for the quantity, not for the loss of lubricant performance. Due to contamination and oxidation, the quality of the oil gradually decreases over time, along with some consumption reducing quantity.

How to Identify Water in Engine Oil ?

According to regulations, the allowable water content in engine oil should be below 0.03%. When the water content exceeds 0.1%, additives such as antioxidants and detergent dispersants will disperse, accelerating the oil's oxidation process. Oxidation produces organic acids that react with acidic oxides from engine exhaust gases and water to form inorganic acids, further increasing engine corrosion. When engine oil contains excessive water, its lubricity worsens, viscosity decreases, leading to premature oil degradation, rusting of parts, or severe mechanical failures like engine seizure or bearing burnout.

Shelf Life The simplest method to check the shelf life of automotive oil is to observe whether its viscosity has changed, the smell has faded, or the color has altered. When observing color changes, pay attention to changes in additives. Additionally, paper filters or electronic instruments can be used to check if the oil's shelf life has expired.

Engine oil is sensitive to moisture in the air, environmental temperature, and light exposure. If exposed to air and strong light for an extended period, it typically becomes ineffective. Using engine oil past its shelf life can significantly damage the car's engine, affecting lubrication and cooling performance.

Many car owners regularly maintain their vehicles, including changing engine oil and oil filters, which are essential maintenance tasks. Let's understand the importance of these two components: 

Engine oil is the lubricant for engine operation, playing roles in lubrication, cleaning, cooling, sealing, and friction reduction. It is significant for reducing wear on engine parts and extending their lifespan. 

The oil filter is a component that filters engine oil. Engine oil contains a certain amount of gelatin, impurities, moisture, and additives; during engine operation, friction between components produces metal filings, air-borne impurities, and oil oxidants, all of which the oil filter targets. Without filtration, direct entry into the oil circuit can adversely affect engine performance and lifespan. 

Car owners often base maintenance on mileage. However, maintenance timing depends on the effective period or mileage of the used oil and oil filter. The shelf life of different brands and grades of mineral oil, semi-synthetic oil, and fully synthetic oil varies; manufacturer recommendations should be followed. Oil filters are generally available in standard and long-life varieties, with standard filters changed alongside the oil, while long-life filters have a longer use period.