What is the meaning of engine oil grade?

[MacLena]

The meaning of engine oil grade refers to the viscosity and quality of the oil. The quality grades for gasoline engine oils are classified as: SA, SB, SC, SE, SF, SG, SH, SJ, SL, SM, with quality increasing from left to right. The 'S' stands for gasoline engine oil, and the following letters represent the grade. The low-temperature viscosity grades are: 0W, 5W, 10W, 15W, 20W, 25W, where a smaller number indicates better cold-start performance at low temperatures. 'W' is the abbreviation for 'winter,' indicating low-temperature performance. For example, 0W oil will freeze at -35 degrees Celsius, while 5W oil will freeze at -30 degrees Celsius.

[SimonLee]

I've been driving for almost twenty years, and understanding oil viscosity grades is like checking clothing sizes. Take the 5W-30 label for example—the number before the W indicates cold-weather fluidity; the lower this number, the smoother the engine starts in winter. Once at -20°C in Harbin, my friend's car with 10W oil just groaned without starting, while my 5W fired right up. The number after W shows high-temperature viscosity, crucial for protecting the engine on highways—older cars often need 40-grade rather than 30 to prevent oil consumption. Letters like SN or SP (starting with S) denote environmental standards; newer cars now use SP-grade, much like updating your phone's OS. Remember, pricier isn't always better—stick to the manual’s recommended grade, as using the wrong one can harm your engine.

[LeJuniper]

Last year when changing the oil for our old Passat, I specifically researched viscosity grades. The initial numbers like '5W' correspond to the oil's performance in cold weather - the smaller the number, the better the low-temperature fluidity. We northern car owners need to pay special attention to this, as 0W starts much faster than 10W when temperatures drop below -10°C in winter. The two-digit number after the dash represents viscosity at high temperatures - from my experience, older German cars work best with 40 weight, while newer Japanese models only need 20. Another easily overlooked detail is the API certification mark - letters like SN or SP inside a small circle. SP is currently the latest standard, especially important for vehicles with particulate filters, as using the wrong grade might clog the exhaust. Always check the maintenance manual before changing oil, and there's often a recommended grade sticker inside the fuel filler cap too.

[Bobby]

The worst thing when repairing cars is customers using the wrong engine oil. The oil grade has three parts to consider: if the low-temperature startup number is incorrect, the engine will struggle to start in cold weather like an asthma patient gasping for air. The 'W' in the middle stands for 'winter,' but ignore it. High-temperature viscosity is the key—common grades like 20, 30, and 40 are like SPF values for sunscreen. Last time, a modified car used a 60-grade oil on the track, and the oil pump couldn't handle it, causing all the bearing shells to burn out. The newly released SP-grade oils contain more detergents, and China-6 vehicles must use them; otherwise, the catalytic converter can fail easily. Here’s a tip: new cars should use the viscosity recommended in the manual, older cars over ten years should go one grade higher, and cars burning oil should directly use 40 viscosity to avoid constantly topping up.

[DeAmir]

The code like 5W-30 on engine oil containers actually has specific meanings. The number 5 before W represents fluidity at -30°C - the lower this number, the better the cold resistance. In Hainan, 10W might suffice, but in Harbin, 0W is preferable. The number 30 after the dash indicates viscosity at 100°C - higher numbers mean thicker oil films. Note that current SP-grade oils are compatible with all gasoline vehicles, while older cars can still use SN-grade. There's also the more niche C3 certification suitable for diesel engines. Don't blindly trust 'full synthetic' labels when changing oil - focus on certification marks instead. One customer used motorcycle oil in their car, resulting in chain tensioner failure within three days - automotive engine oils contain completely different additives to withstand combustion contamination.

[VanGabriella]

For frequent construction site drivers, choosing the wrong engine oil viscosity can indeed lead to breakdowns. The number before the W indicates cold-start performance—once I cheaped out with 10W-40 oil, and at -10°C, the battery warning light flickered wildly as the starter couldn't crank the thickened oil. High-temperature viscosity matters too—a friend used SAE 40 in his new car and fuel consumption jumped by 2L/100km. Modern SP-grade oils now contain timing chain protectors, outperforming older SN-grade in durability. Pro tip for reading labels: GF-6A certified oils suit Japanese/Korean models best, while European cars require A3/B4 approval. Never mix different brands—I once saw someone blend 5W-20 with 0W-40, resulting in sludge so severe the engine looked like a coal mine when disassembled.