What does 20w-40 engine oil mean?
3 Answers
20w40 engine oil represents the grade of the oil, where the number before W indicates the minimum starting temperature, meaning 20W represents the ability to start at a minimum temperature of -15°C. The number 40 represents the maximum applicable temperature in summer, with higher numbers indicating a higher maximum usage temperature in summer. Relevant information about engine oil is as follows: 1. Introduction: Engine oil, also known as engine lubricant, English name: Engine-oil. With a density of approximately 0.91×10³ (kg/m³), it serves to lubricate and reduce friction, assist in cooling, seal against leaks, prevent rust and corrosion, and provide shock absorption for the engine. It is hailed as the "blood" of the car. 2. Composition: Engine oil consists of base oil and additives. Base oil is the main component of lubricating oil, determining its basic properties, while additives can compensate for and improve the shortcomings of the base oil's performance, imparting certain new properties, making them an important part of lubricating oil.
The 20W-40 oil is what I've often encountered driving older cars for years. The numbers on the label primarily indicate viscosity. The 20W part refers to low-temperature flow performance, where W stands for winter, meaning it can remain fluid at around -20°C, making winter starts less strenuous. The 40 is the high-temperature viscosity grade, ensuring the oil doesn't thin out too much when the engine heats up, thus preventing rapid wear on components and extending engine life. The advantage of multi-grade oil is its year-round usability, eliminating the need for frequent changes like single-grade oils, making it particularly suitable for temperate regions. Where I live, with significant climate variations—summer temperatures exceeding 40°C while driving uphill—this oil maintains stable oil pressure. Winter starts around freezing are relatively smooth, though it might not perform as well in places like Northeast China. Remember to regularly check the oil color and level, changing it every 5,000 kilometers or six months for smoother operation in older engines. Always refer to the vehicle manual when selecting oil, and avoid switching to lower viscosity oils casually, as it may increase wear risks.
I usually help friends with car repairs, and the 20w-40 label commonly seen on oil bottles refers to the viscosity code. The first number, 20, indicates low-temperature fluidity—the smaller the better, ensuring it doesn’t solidify in cold weather, like at -15°C. The 40 represents thickness at high temperatures, with higher numbers offering stronger lubrication and protection when hot. This combination is a multi-grade oil, widely adaptable, covering everything from cold starts to high-speed engine operation. When checking it, if the oil discolors or contains metal shavings, it’s time for a change to prevent accumulated wear. It works well in moderate climates but may cause slight sluggishness in extreme cold; at high temperatures, the 40 viscosity reduces fuel consumption fluctuations at the cost of slightly higher oil consumption. My advice is to first consider the car’s age and mileage when choosing oil—older cars suit higher viscosity like 40, while newer ones can try 30 or below for better fuel efficiency. Don’t skimp on routine maintenance; change the oil on time to avoid major repairs.
