Depending on the source crop, biodiesel fuels exhibit varying levels of low-temperature performance. Biodiesel consists of a mixture of long-chain fatty acid esters (usually fatty acid methyl esters, or FAMEs) that differ in carbon chain length and degree of saturation. The individual components of this mix have melting points somewhere between -35°C and +45°C, a very wide range. Biodiesel derived from different sources (such as soy, palm, tallow, etc.) contains different relative levels of these components, which accounts for the variance in biodiesel cold flow properties.
The greatest influence on cold flow properties is the relative quantities of the lower melting point components (mainly unsaturated and lower molecular weight saturated) compared to the components with a higher melting point (mainly higher molecular weight saturated). As the low-temperature performance of most biodiesel fuels is inferior to that of fossil diesel, it is important to improve biodiesel cold filter plugging point, cloud point, and pour point properties so that biodiesel meets the performance standards of current fuel specifications.
Biodiesel can also suffer from oxidation and is typically less stable than modern middle distallates.The aging process can happen within hours or days, depending on the crop source, the quality and the type of manufacturing process. Biodiesel should be treated with oxidation stabilizers to avoid any problems from aging.