What is the Definition of Motor Oil Grade?

[LeViolet]

Motor oil grade refers to the classification of oil's application range. Below are detailed introductions to motor oil grades: Grade Classification: The composition of motor oil grades includes two parts: classification and viscosity specifications. Oil classification is represented by a combination of two letters. Those starting with "S" are for gasoline engines, those starting with "C" are for diesel engines, and those with both "S" and "C" are universal oils for both gasoline and diesel engines. Generally, they are arranged in alphabetical order, with letters further back indicating higher quality grades. The following grade represents oil viscosity; the smaller the number, the better the fluidity in low-temperature environments, and the lower the usable environmental temperature, meaning better engine protection during cold starts. Seasonal Classification: High-Temperature Type: The larger the number representing viscosity at 10 degrees, the higher the viscosity. Low-Temperature Type: "W" indicates use only in winter; the smaller the number, the lower the viscosity and the better the low-temperature fluidity. All-Weather Type: Indicates that the viscosity grade at low temperatures meets the requirements of SAE15W, 10W, and 5W, and the viscosity grade at high temperatures meets the requirements of SAE40 and 50, belonging to the universal type for winter and summer.

[DiGrant]

I often get asked by friends about what engine oil viscosity ratings mean, such as the common 5W-30 format. Simply put, oil viscosity ratings are based on the SAE viscosity standard, which classifies the fluidity of oil at different temperatures. The 'W' stands for Winter, and the preceding number, like 5, indicates low-temperature viscosity—the smaller the number, the better the fluidity in cold weather, making it easier to start the engine at, say, -30°C. The number after, like 30, refers to high-temperature viscosity—the larger the number, the stronger the protection at 100°C, preventing excessive engine wear. This rating is crucial because it directly relates to engine lubrication effectiveness—choosing the wrong one may lead to hard starts, increased fuel consumption, or shortened engine lifespan. I recommend strictly following the manual's recommendations for new cars, such as modern vehicles often using low-viscosity oils like 0W-20 for improved efficiency, while older cars may use 10W-40 to reduce leakage risks. Also, consider local climate conditions—prioritize lower 'W' numbers for colder winters to ensure smooth daily operation.

[AbelLee]

The viscosity rating is key when choosing engine oil. I usually refer to formats like 5W-40 for selection. The lower the number before W, the better the oil flows during cold starts—for example, 0W oil is ideal for ignition in frigid northern winters. The higher the number after W provides stronger protection when the engine is hot, preventing component wear. Selecting the right viscosity isn't just about the numbers; you must also consider your car's age and driving conditions—for instance, 5W-30 saves fuel for short urban commutes, while 40-grade viscosity offers stability for long highway drives. From experience, I've learned that randomly choosing the wrong viscosity carries risks: low W-number oils thin out in hot weather causing noise, while high post-W numbers lead to slow starts in cold climates. It's best to change oil every 5,000 km to maintain viscosity quality and protect that beloved engine for long-lasting operation. During routine maintenance, simply checking the manual for recommended values is quick and reliable.

[ArabellaLee]

The oil grade, such as 5W-30, defines the viscosity rating. The 'W' stands for winter, with the first number indicating cold-weather fluidity—lower numbers like 5 represent thinner oil for easier starts. The second number, such as 30, denotes high-temperature thickness to protect a hot engine. This grading system helps car owners select the right oil to ensure proper lubrication, preventing wear or fuel consumption issues. Newer cars benefit from low-viscosity oils like 0W-20 for improved efficiency, while older vehicles may opt for 10W-40 to reduce leaks. Seasonal changes also call for timely oil swaps to safeguard critical components. I emphasize never ignoring the manual's recommendations—simple steps make maintenance smoother.