What Do the Numbers on Engine Oil Represent?
3 Answers
The numbers on engine oil represent the following: 1. The number before the 'W' indicates the oil's viscosity under low-temperature conditions; 2. The number after the 'W' represents the kinematic viscosity standard at 100 degrees Celsius. The functions of engine oil include: 1. Lubrication; 2. Assisting in cooling; 3. Cleaning; 4. Sealing and preventing leaks; 5. Rust and corrosion prevention; 6. Shock absorption and anti-wear. Engine oil can be categorized based on usage conditions: 1. Diesel engine oil: Selected according to the total mechanical and thermal load of the car engine and the severity of engine operating conditions; 2. Gasoline engine oil: Chosen based on the severity of engine operating conditions, additional devices in the car's intake and exhaust systems, and the production year.
The numbers in engine oil actually indicate viscosity grades, such as 5W-30. The 'W' stands for winter, and the smaller the first number, the better the low-temperature fluidity, making engine starts smoother in sub-zero weather. The second number represents high-temperature viscosity; the higher the value, the thicker the oil film at high temperatures, preventing wear. These are designed based on SAE standards to help the oil maintain a balanced performance between cold and hot conditions. Different cars have different needs: northern winters are suitable for oils starting with 0W or 5W, while southern summers can use higher second numbers like 40. Sports cars use high viscosity to prevent high-temperature damage, while family cars can use medium viscosity. Choosing the wrong numbers can cause problems, such as low 'W' oils being too thin in hot weather, leading to insufficient protection and part damage, or high numbers causing excessive viscosity in cold weather, making the motor hard to start. The key is to follow the vehicle manual's recommendations to avoid unnecessary trouble and expenses.
As an average car owner, I focus on how to practically use the numbers on engine oil. It's called the viscosity grade, and 5W-30 indicates low-temperature fluidity and high-temperature protection. A lower W number means quicker starts in winter, while a higher second number ensures stronger lubrication in summer. Adjust according to the season: use 0W-20 or 5W-30 in cold winters and switch to 10W-40 in summer to prevent overheating. For city driving, 30 or 40 numbers are cost-effective; for off-roading or heavy loads, opt for higher protection. Always check the manual for the recommended oil when changing—wrong choices may increase fuel consumption or engine noise. A good practice is to check oil levels every six months and change if the color darkens; synthetic oil lasts longer and is more eco-friendly. A simple tip: compare prices and choose reputable brands when shopping online for worry-free safe driving.
