- Method ASTM D2500
- Repeatability 2° C
- Reproducibility 3° C
- Blending non-linear
- Additive Correction Yes
This test method covers only petroleum products and biodiesel fuels that are transparent in layers 40 mm in thickness, and with a cloud point below 49°C. Most of these fuels are No2 fuel oil (diesel).
The purpose of this test is to determine when the waxes or paraffins will freeze up and drop out of the fuel. This is important to colder areas where Diesel is used or stored. When the temperature of the fuel drops below the Cloud Point it can cause issues such as blocked filters, clogged pumps, and no start conditions in vehicles.
The method is performed by adding fuel to a glass jar and placing a thermometer on the top that hovers right over the bottom of the jar. The sample is then cooled and checked every 1°C until a thin cloudy layer covers the entire bottom of the jar.