How to Identify Motor Oil Grades?

[McPreston]

On the outer packaging of motor oil, you can find the SAE and API labels. SAE stands for the Society of Automotive Engineers, while API stands for the American Petroleum Institute. The grade following SAE indicates the viscosity value of the oil, and the grade following API indicates the quality level of the oil. Below is a detailed introduction: 1. SAE Classification: SAE-classified oils are generally labeled as 0W-20, 0W-30, 0W-40, 5W-20, 5W-30, 5W-40, 5W-50, 10W-20, 10W-30, 10W-40, 10W-50, etc. 2. API Classification: API-classified oils are divided into two types, those starting with S and those starting with C. S represents gasoline engine oils, with specifications including: API SA, SB, SC, SD, SE, SF, SG, SH, SJ, SL, SM, SN. C represents diesel engine oils, with specifications including: API CA, CB, CC, CD, CE, CF, CF-2, CF-4, CG-4, CH-4, CI-4.

[Phil]

Last time I helped a friend choose engine oil, I specifically researched the viscosity grade issue. The oil grade, like 10W-40, is a combination where the number before the W represents winter low-temperature fluidity - the smaller the number, the smoother cold starts will be. For example, 0W remains fluid even at -30°C. The 40 after represents high-temperature viscosity - during high-speed driving, the oil needs to be sufficiently thick to protect the engine. When changing oil, you must check the maintenance manual requirements. Japanese cars commonly use 0W-20, while German cars mostly use 5W-40. Choosing the wrong grade may increase fuel consumption or accelerate wear, especially for older cars where blindly using low-viscosity oil can actually lead to oil burning. Nowadays, full synthetic oils cover a wider range of grades, and their winter cold starts are noticeably smoother than mineral oils.

[McDaniel]

Based on my years of driving experience, the SAE rating on the oil container is crucial. The number before the letter W indicates low-temperature performance; for example, 5W is more cold-resistant than 10W. The number after the dash represents high-temperature protection capability. A viscosity of 30 is sufficient for city commuting, while a 40 is better for frequent long-distance driving. Friends in the north must pay attention to the number before W in winter—using 0W in sub-zero regions ensures smooth cold starts without engine strain. If you notice the old oil is too thin during an oil change, consider switching to a higher viscosity rating. However, if the engine is leaking oil, you should actually reduce the viscosity. Many repair shops now have viscosity reference charts—if unsure, simply provide your car model for them to check, which is the safest approach.

[AnastasiaAnn]

The oil viscosity ratings are quite interesting from a performance perspective. A lower winter number indicates better cold-weather pumpability, reducing cold-start wear by over 70%; while a higher summer number represents stronger oil film strength. But don't choose based solely on numbers - using high-viscosity oil in naturally aspirated engines increases fuel consumption, while low-viscosity oil in turbocharged engines may provide insufficient sealing. The newly introduced SP-grade oils even contain detergents that can extend oil change intervals. In one test comparing the same brand's 5W-30 and 0W-40 oils, the viscosity difference at high temperatures was like comparing honey to syrup. Using the wrong grade in older vehicles can significantly increase sediment buildup in the oil pan.

[StTravis]

I'm used to comparing new and old engine oil by dripping them on paper. Fully synthetic oil shows clear and distinct diffusion rings, while semi-synthetic oil appears slightly cloudy. Just check the SAE grade marked on the container - major brands all use unified SAE standards. Pay special attention to significant seasonal differences in oil selection. If you experience hard starts in winter, switch to a lower-temperature grade. Last time I used the wrong high-viscosity oil, my fuel consumption increased by 1L immediately. Although counterfeit oil may show the same grade, its fluidity is much worse - it solidifies at -15°C in the freezer. Take the OEM maintenance manual's grade recommendations seriously, as unauthorized grade changes may void your warranty.

[IsabellaLynn]

Three key points to identify engine oil grades: Choose smaller numbers for cold starts, and select high-temperature protection numbers based on needs. Mineral oils are typically 10W-40, while full synthetics can achieve 0W-20. Select grades according to climate—5W-30 is sufficient year-round in the south, while 0W is a must in the northeast. The API rating (e.g., SP) on the oil can indicates the latest technical standards; pairing it with the right grade yields better results. Long-term use of incorrect grades triples carbon buildup risks—I've seen cars running 15W-50 in urban areas with sludge-filled valve covers. Nowadays, smart oil sensors monitor viscosity changes in real time, offering more intuitive feedback than grade labels.