What is the optimal temperature for lubricating oil viscosity testing?

1. Why does viscosity testing need to determine the temperature?

To detect the viscosity of lubricating oil, we select a temperature and measure at that temperature, because the viscosity changes with temperature. The same lubricating oil has different viscosities measured at different temperatures. As the temperature rises, lubricating oil becomes thinner and its viscosity decreases. When the temperature decreases, the viscosity of lubricating oil increases and the oil thickens.

2. Check the viscosity, 40 degrees or 100 degrees?

At present, the viscosity of lubricating oil is generally measured at 40°C or 100°C. The specific viscosity at 40°C or 100°C depends on the specific situation and is not a random measurement.

Regarding the measurement temperature of viscosity, it is best to be close to the operating temperature of the equipment. Generally speaking, the viscosity of industrial lubricants is measured at 40°C because the operating temperature of industrial equipment is relatively close to this range.

In addition, the viscosity changes of lubricating oil are relatively more significant at low temperatures. Therefore, if you want to detect viscosity changes caused by some abnormal factors, such as water in the lubricating oil, mixed fuel, viscosity changes caused by oxidation, etc., the viscosity changes caused by oxidation at 40°C It is relatively easier to detect.

However, the operating temperature of some equipment is relatively high. In order to keep the detection temperature close to the use temperature, we should detect the viscosity at high temperature. For example, in automobile engines, the viscosity is usually detected at 100°C.

3. Calculate the viscosity index of lubricating oil:

Some equipment may experience large temperature changes during operation. In this case, we need to measure a high temperature viscosity and a low temperature viscosity. For example, multi-grade oil is used in lubrication situations with large temperature changes. The viscosity of multi-grade oil is measured at two temperatures, one high temperature viscosity and one low temperature viscosity. From these two viscosities, we can calculate the viscosity index of the lubricating oil. For situations where the temperature changes greatly during operation, the viscosity index of the lubricating oil is a very important indicator. A high viscosity index indicates that the viscosity of the lubricating oil is relatively more stable during temperature changes.

4. Summary:

In short, when testing the viscosity of lubricating oil, you need to clarify these issues:

· The temperature at which the equipment is operating normally.

· Will there be large temperature fluctuations (greater than 20-30℃) during the operation of the equipment?

· If the viscosity is to be compared with other oil samples, the measurement conditions (including temperature) should be consistent.