What does 20w40 engine oil mean?
1 Answers
20w40 engine oil, where 'w' stands for winter, indicates the oil's performance characteristics. The number before 'w' represents the oil's low-temperature fluidity—the smaller the number, the better the fluidity in cold conditions. The number after 'w' denotes the oil's viscosity grade at 100 degrees Celsius, with higher numbers indicating better protection for the engine at high temperatures. Engine oil is the lubricant used in engines, composed of base oil and additives. It serves multiple functions, including lubrication, reducing friction, aiding in cooling, sealing against leaks, preventing rust and corrosion, and cushioning impacts. Based on the base oil, engine oils can be categorized into two types: mineral oil and synthetic oil. Synthetic oils are further divided into full synthetic and semi-synthetic. Lubricant base oils are primarily classified into mineral base oils and synthetic base oils.