How are engine oil grades classified?

[MacGabrielle]

Engine oil grades are classified based on viscosity values. The method for checking engine oil is as follows: 1. Locate and pull out the oil dipstick in the engine compartment, then wipe off the oil traces on it with a cloth; 2. Reinsert the oil dipstick and slowly pull it out again to check the oil traces on the dipstick; 3. If the oil trace is between the upper and lower limit marks, the oil level is appropriate. If the oil trace is very close to or below the lower limit mark, oil should be added as soon as possible. When the oil is overfilled beyond the upper limit, the excess oil should be drained from the oil pan. The functions of engine oil include: lubrication, auxiliary cooling, cleaning, sealing and leak prevention, rust and corrosion prevention, shock absorption, and anti-wear.

[CaydenLynn]

Over the years, I've interacted with many car owners and found that viscosity grade and API standard are the most commonly considered factors when choosing engine oil. The viscosity grade is the numerical combination like 5W-30 printed on the packaging. The smaller the number before W, the better, especially for cold starts in winter - 0W starts much smoother than 10W. The number after W represents high-temperature viscosity, with Japanese cars typically using 20 or 30, while German cars prefer 40. For API standards, check the alphabetical order - most new cars now require SP grade, which offers better cleaning performance than the older SN grade. A friend insisted on using cheaper SL-grade oil for 50,000 kilometers, resulting in severe engine carbon buildup. I recommend directly purchasing the grade specified in your maintenance manual and avoiding downgrading oil quality arbitrarily.

[BradyRose]

Many car owners are confused about the meaning of motor oil grades during car maintenance. Simply put, motor oils are divided into winter-summer multi-grade and single-grade types, with most being multi-grade like 10W-40 nowadays. The number before the W indicates cold-start performance. In my hometown Harbin where temperatures drop to -30°C in winter, 5W oil starts the engine noticeably smoother than 10W. The number 40 after represents high-temperature viscosity, which must match the engine. Older off-road vehicles perform better with 50 viscosity for protection, but using overly thick oil in regular sedans increases fuel consumption. Also, don't overlook API certification marks - for instance, the latest SP grade offers 40% more wear protection for turbocharged engines compared to SN grade.

[AddysonAnn]

In the tuning community, selecting engine oil is particularly focused on performance balance. Those pursuing extreme driving opt for 0W grades to ensure cold-start RPM, while high-temperature viscosity is chosen based on engine reinforcement levels. Factory naturally aspirated cars find 30 viscosity the most economical, while turbocharged vehicles with ECU tuning are recommended to use 40 or higher viscosity to maintain oil film strength. For API ratings, only the latest SP grade is considered, offering improved oxidation stability and deposit control over older standards. Interestingly, racing oils are now trending toward 0W-50 formulations, balancing low-temperature fluidity and high-temperature protection. Remember not to be fooled by packaging—ACEA or ILSAC certifications are more reliable indicators.

[AnaFitz]

The classification of engine oil mainly depends on two systems: SAE viscosity grading and API quality rating. The former is like 5W-30; I recommend starting with 10W in the south and using 0W or 5W in the north. The latter is letter combinations like SL/SP, and the current minimum standard is SN grade. Here's a money-saving tip: although full synthetic SP-grade oil is more expensive per unit, its oil change interval is 50% longer than mineral oil, making it more cost-effective in the long run. After driving an old car for ten years, I found that engines with over 150,000 kilometers need higher viscosity oil to compensate for wear gaps, such as switching from 5W-30 to 5W-40. When choosing engine oil, also consider the base oil type; Group III hydrocracked oil offers the best cost-performance ratio.

[MacSamantha]

Having experienced a major engine overhaul due to incorrect oil selection, I now place great emphasis on grade matching. For new cars, I directly choose the viscosity specified in the manual, usually 0W-20 or 5W-30. For API grades, I always buy SP-rated oil, which provides better timing chain wear protection than SN grade. A common misconception is that lower cold-temperature viscosity saves fuel, but in reality, the number before the 'W' only affects cold starts – fuel economy primarily depends on high-temperature viscosity values. I've tested the same car model using both 0W-20 and 5W-20 oils, and the fuel consumption difference was less than 0.5L. Additionally, it's important to pay attention to oil certification standards: European cars require ACEA A3/B4 certification, while American and Japanese vehicles follow the ILSAC GF-6 standard.