How are oil grades classified?

[VonBryce]

Oil grade classification methods: S represents oil for gasoline engines, C represents oil for diesel engines. Then, following the English alphabetical order after the letters S and C, from SA to SL, the later the English letter appears in the alphabet, the higher the oil grade, indicating better performance of the oil. The S series represents oil specifications for gasoline engines: SA, SB, SC, SD, SE, SF, SG, SH. The C series represents oil specifications for diesel engines: CA, CB, CC, CD, CE, CF, CF2, CF4, CG4, CH4, CI4. When both S and C letters are present, it indicates that the oil is suitable for both gasoline and diesel engines. Oil is the lubricant used by engines, composed of base oil and additives.

[VanCamilla]

As a veteran driver with twenty years of experience, let me talk about the tricks in engine oil. The grading of engine oil mainly depends on the API rating, such as the common SP and SN letter combinations nowadays—the further back the letter, the newer the oil. Then there’s the SAE viscosity, like 5W-30. The number before the W represents low-temperature fluidity (5W handles cold better than 10W), while the numbers 30 or 40 after it indicate high-temperature protection. I’ve been using 5W-30 in my car year-round, and even at minus twenty degrees in winter, the engine starts without a hitch. Recently, I heard that China VI vehicles now require low-ash engine oil to prevent clogging the particulate filter.

[SanStephanie]

Last week, I finally understood the oil grading standard when changing my car's oil. In the SAE rating of motor oil, for example, 0W-20, the '0W' indicates winter low-temperature performance—the smaller the number, the smoother the cold start. The '20' represents high-temperature viscosity—the larger the number, the thicker the oil. Common full synthetic oil like 5W-30 is more moderate, while 0W-20 is more fuel-efficient for new cars. The mechanic said turbocharged cars are best suited for oils with SP certification due to their stronger anti-wear properties. Remember not to mix oils randomly—last time my friend mixed 5W-40 into 0W-20, and the engine immediately sounded like a tractor.

[Corbin]

Engine oil grading is actually quite intricate. The internationally recognized standard is the API certification system, with SP being the current highest grade, offering improved chain protection and turbocharger protection compared to the older SN grade. In terms of viscosity grading, 0W series can maintain fluidity at -35°C, making it particularly suitable for northern regions. For southern areas, 5W or 10W is sufficient. The most common issue I encounter during repairs is owners using the wrong viscosity, such as older cars using low-viscosity 20-grade oil leading to oil burning. German cars generally require 40 viscosity, while Japanese cars mostly use 20.

[MacReese]

Choosing the right engine oil for your car is similar to selecting skincare products. The SAE grade is like skin type attributes (0W for oily skin, 10W for dry skin), while the API rating corresponds to serum concentration (SP is more nutrient-rich than SN). For my naturally aspirated compact car, SP-grade 5W-30 is just right, whereas my neighbor's turbocharged vehicle upgraded to 0W-40. A special reminder for hybrid owners: since oil warms up slowly during pure electric driving, low viscosity should be chosen to prevent emulsification. The last maintenance sheet from the 4S shop mentioned ILSAC GF-6 standard, claiming it's a fuel-saving formula.

[SanNicole]

Engine oil grading has hardcore indicators: 1. API rating depends on phosphorus & zinc content—SP grade requires < 0.08% to protect catalytic converters; 2. SAE viscosity focuses on HTHS (High-Temperature High-Shear)—turbocharged engines need > 3.5cP; 3. Also check ACEA European standards like C5-certified 0W-20 oils with low SAPS. Lab tests show 30-grade oils' kinematic viscosity at 100°C ranges 9.3-12.5mm²/s. China-6 vehicles mandate SP/GF-6 low-ash oils—DPFs clog within 6 months otherwise.