How to Distinguish the Quality of Engine Oil?
2 Answers
Engine oil is classified by quality grade and viscosity grade. The quality grade adopts the classification standard set by API, while the viscosity grade uses the classification established by SAE. The classification of engine oil is as follows: 1. Viscosity index: According to the SAE method, engine oils are categorized into 6 types for winter, 5 types for summer, and 16 types suitable for both winter and summer. Winter oil grades include OW, 5W, 10W, 15W, 20W, and 25W. The symbol W stands for winter, and the smaller the number before W, the lower the low-temperature viscosity, the better the low-temperature fluidity, and the lower the applicable minimum temperature. Summer oil grades are 20, 30, 40, 50, and 60. The larger the number, the higher the viscosity and the higher the applicable maximum temperature. All-season oil grades include: 5W/20, 5W/30, 5W/40, 5W/50, 10W/20, 10W/30, 10W40, 10W/50, 15W/30, 15W/40, 15W/50, 20W/20, 20W/30, 20W/40, and 20W/50. The smaller the number representing the winter part and the larger the number representing the summer part, the wider the applicable temperature range. 2. Quality index: According to the API quality classification method, engine oils are divided into the gasoline engine oil series (S series) and the diesel engine oil system (C series). Each series of oils is arranged in alphabetical order (A, B, C, D, E, F) and divided into several grades. The later the letter, the higher the grade.
After the last oil change, the car starts much smoother. Telling good oil from bad is actually quite simple: high-quality oil pours out clear like honey, with no impurities or sediment. Sniff it up close – it shouldn’t have a pungent smell; any sour or burnt odor means it’s no good. Genuine products come in refined packaging with tight seals, and checking the anti-counterfeit code is the safest bet. I usually rub a bit of oil between my fingers – good oil feels highly lubricating without being sticky, while poor-quality oil turns rough when rubbed. When checking the dipstick on a cold engine, uniform oil film coating is a good sign. Oh, and always check for major certification labels like SN PLUS or SP – higher grades offer better protection. Don’t cheap out on no-name brands; one engine repair could cost you a decade’s worth of premium oil.
