What Do Engine Oil Parameters Mean?
3 Answers
Taking 5W40 as an example: The letter 'W' stands for winter, indicating low temperature. The number '5' before 'W' represents the low-temperature fluidity of the oil—the smaller the number, the better the oil's low-temperature fluidity. The number '40' after 'W' represents the high-temperature viscosity—the larger the number, the better the oil's high-temperature viscosity. Method for Changing Engine Oil: Loosen the nut at the bottom of the transmission oil pan to allow the old transmission oil to drain out naturally by gravity. Connect the transmission to a circulation machine via a pipeline interface, and the new transmission oil will push out the old oil under pressure. Methods to Determine if Engine Oil Needs Replacement: Pull out the dipstick and smell it closely. If there is a strong sour or foul odor, it indicates the oil has deteriorated and should be replaced. Rub the extracted old oil repeatedly between your thumb and forefinger. If you feel impurities, poor viscosity, or even a gritty sensation, it should be replaced. Hold the dipstick at a 45-degree angle under light and observe the oil droplets. If there are no metal particles in the droplets, the oil is in good condition. If there are many metal particles, the oil should be replaced.
The alphanumeric combinations on engine oil packaging actually have specific meanings. Taking the most common 5W-30 as an example, the 5W at the beginning represents low-temperature fluidity - the smaller the number, the smoother cold starts will be. The 30 after W indicates high-temperature viscosity, with higher numbers offering better protection under heat. API grades starting with S denote gasoline engine oils, with SN being the current highest standard. Markings like ACEA A5/B5 represent European automaker certifications. Base oils are categorized into three grades: mineral, semi-synthetic, and full synthetic. When I chose oil last month, I paid special attention to these parameters - while full synthetic is more expensive, it provides better protection for turbocharged engines. Different vehicle models have quite varied oil requirements, with older cars potentially needing higher viscosity oils.
Understanding oil specifications is crucial during every maintenance session, as it directly impacts engine longevity. The first two digits followed by 'W' indicate low-temperature performance; for example, 0W oil can flow at -35°C. The last two digits represent viscosity at 100°C—Japanese cars often use 20-weight oil, while German vehicles typically require 30 or 40-weight. Letters like SM/SP on the bottle denote API (American Petroleum Institute) oil quality standards. I remember my uncle's decade-old car consistently used the wrong oil, resulting in severe sludge buildup when the engine was opened. The owner's manual provides the most accurate guidance, as manufacturers specify recommended parameters. Turbocharged vehicles may require shorter oil change intervals.
