The low temperature fluidity of diesel is a very important performance for biodiesel engines operated in open air, especially at low temperatures. The freezing point of biodiesel fuel does not indicate the minimum temperature that biodiesel may be used because it begins to crystallize wax at temperatures above 5-10°C. Although the oil has a certain degree of fluidity, it is possible to block the oil pipeline and filter and then causing fuel interruption.

Using of cloud point, pour point or cold filter point to express the low temperature fluidity of biodiesel and provisioning that the indicators are selected according to region and season reflects the usage of biodiesel at low temperature. Usually we specify that the cloud temperature is 6 ℃ higher than the minimum temperature in the where biodiesel is used.

Cold filter point: It refers to the maximum temperature at which it is less than 20ml per minute when the test oil going through the filter, and the temperature has a good correspondence with the actual use of the boundary temperature and has been widely used. China also intends to combine the temperature conditions to determine the cold filter point or pour point of diesel as a fuel flow indicators at low temperature according to the region and season.

Cloud point: It refers to the temperature at which the light oil (including diesel) becoming turbid from transparent under the conditions of the cooling process. The reason for generating turbidity is that the n-alkanes begin to form tiny grains at low temperatures which cannot be observed with the naked eye.

Pour point: It refers to the temperature that the temperature at which placing the tubes flat for 5 seconds without the sample flowing pluses 3.