What does the pour point of lubricating oil mean?
3 Answers
The pour point refers to the lowest temperature at which an oil sample can flow under specified test conditions when cooled; the freezing point refers to the highest temperature at which the surface of the cooled oil sample no longer moves under specified test conditions, both expressed in °C. Here is some related information: 1. Pour point: The physical significance of the pour point is one of the parameters reflecting the low-temperature fluidity of the oil. The lower the pour point, the better the low-temperature fluidity of the oil. Fuel oil has a technical indicator called the pour point, measured in °C. Generally speaking, the so-called pour point of fuel oil refers to the lowest temperature at which it can flow. 2. Freezing point of lubricating oil: The solidification of oil is quite different from that of pure compounds. Oil does not have a clear solidification temperature; the so-called "solidification" only means that the liquid surface as a whole loses fluidity. The freezing point is a quality indicator for diesel and lubricating oil that describes low-temperature fluidity. Its level is related to the chemical composition of the oil. Lighter fractions have lower freezing points, while heavier fractions and higher wax content result in higher freezing points.
For me, the pour point of lubricating oil means the lowest temperature at which it can still flow smoothly. I remember when I lived in a northern city, one winter my car wouldn't start no matter what. The mechanic checked and said it was because the engine oil had solidified—the pour point was too high. Simply put, if the pour point is too high, when the weather gets too cold, the oil becomes thick and hard to flow, and the engine parts don't get lubricated when running, leading to wear or even seizing. Later, I learned to choose oil by checking the pour point value on the packaging. For regular areas, -15°C to -25°C is fine, but in snowy regions, you need low-temperature oil with a pour point below -35°C. It's not just about starting trouble—this issue also affects engine lifespan and fuel consumption. Regularly checking the oil condition and changing it according to the season can save a lot on repair costs. I've seen friends ignore this and end up spending tens of thousands on major engine repairs. So, even though the pour point seems like a small indicator, preventing problems before they happen is crucial.
I'm a seasoned expert in solving cold start issues. Simply put, the pour point of lubricating oil is the lowest temperature at which it can still flow. If it's too high, the oil will freeze in cold weather, turning into a paste-like substance, causing excessive friction and damaging the engine when it starts. I always advise car owners to pay attention to the pour point value on the oil container label. For areas like North China, choose oils with around -20°C, while for the severe winters in Northeast China, opt for below -30°C. It's not just temperature that affects it; aging oil or mixing with inferior quality oil can also make the pour point substandard. During inspections, check the low-temperature fluidity by feeling some used oil. Choosing the right pour point makes engine starts much smoother, saving money and providing peace of mind. I also remind fellow car enthusiasts that pre-winter oil changes are the golden period—don't skimp for the sake of cheapness or convenience. Mishandling pour point issues can lead to wear and tear at best, or a complete engine shutdown at worst.
