what happens when you cool biodiesel. petroleum-based diesel fuel, and vegetable oil?

When you cool biodiesel, petroleum-based diesel fuel, and vegetable oil, they undergo different changes due to their chemical compositions.

1. Biodiesel: Biodiesel is a renewable, clean-burning fuel made from vegetable oils or animal fats. When you cool biodiesel, it starts to solidify and eventually forms crystals. The temperature at which biodiesel starts to crystallize is called the cloud point. As the temperature further decreases, the solidified biodiesel can turn into a gel-like substance, which is known as the gel point. The gel point indicates that the fuel can no longer flow and may cause issues with fuel filters and injectors in low-temperature conditions.

2. Petroleum-based Diesel Fuel: Petroleum-based diesel fuel, also known as petrodiesel or fossil diesel, is derived from crude oil. When you cool petrodiesel, it also undergoes changes in its properties. Similar to biodiesel, petrodiesel has a cloud point and a gel point, although the exact temperatures may vary depending on the blend and additives used in the fuel. As the temperature drops below the cloud point, waxy components in petrodiesel start to solidify, which can lead to filter clogging and fuel flow issues at lower temperatures.

3. Vegetable Oil: Vegetable oil, such as soybean oil or canola oil, does not undergo the same level of refinement as biodiesel or petrodiesel. When cooled, vegetable oil behaves differently compared to the other fuels. At low temperatures, vegetable oil tends to thicken and become more viscous, but it does not solidify completely like biodiesel or petrodiesel. This increased viscosity can make it challenging to pump and inject the vegetable oil as fuel, especially in cold weather.

It's essential to consider the cold flow properties of these fuels, as they can affect the performance and operability of diesel engines in colder climates. To mitigate these issues, various additives, such as flow improvers or cold flow enhancers, can be blended with biodiesel or petrodiesel to lower the cloud point and improve low-temperature operability.