Biodiesel has been widely accepted as a blend for compression ignition engines and offers many advantages including: higher cetane number; reduced exhaust emissions; reduced toxicity; improved safety; and lower lifecycle CO₂ emissions. A characteristic of biodiesel that has limited its use is its relatively poor low-temperature properties, which are largely a function of the fatty acid make-up of the oil feedstock. Highly unsaturated fatty acid esters offer improved low-temperature properties at the expense of reduced ignition quality and reduced oxidation stability. Additives designed for petroleum diesel have been used with limited success and specific additives for biodiesel remain in their infancy. The addition of branched moieties either to the alkyl head-group of the ester or as a side-chain to the tail-group can dramatically reduce cloud point (CP) without significantly changing the fatty acid profile.

Conventional biodiesel was synthesised from vegetable oil and various alcohols including; methanol, ethanol and butanol. Alkoxyl groups were added at the π-bonds of the unsaturated esters. The success and extent of substitution was confirmed by gas chromatographic analysis. Cloud point determinations were performed for both pure alkoxylated biodiesel and blends with unsubstituted biodiesel. The relationship between the fraction of alkoxylated biodiesel and cloud point was determined for a range of blends. Significant improvement in low-temperature performance of biodiesel was evident from the large reductions in CP.