A property of biodiesel that currently limits its use to blends of 20% or less is its relatively poor low-temperature properties. Alkoxylation of the unsaturated portion of biodiesel offers the potential benefit of reduced cloud point without compromising ignition quality or oxidation stability. Conventional biodiesel was synthesised from canola oil and the alcohols methanol, ethanol and butanol, epoxidised in situ, and alkoxylated by acid-catalysed oxirane ring opening in the presence of the alcohol of the ester group. Optimal conditions for epoxidation were H(2)O(2)/biodiesel molar ratio of 2: 1, acetic acid/biodiesel molar ratio of 0.2:1, 2 wt% H(2)SO(4), 6 h reaction at 60 degrees C. Alkoxylation resulted in alkoxy substitution rates of 37.1% (methyl), 34.3% (ethyl) and 32.9% (butyl). Selectivity for alkoxy biodiesel was 89.0%, 82.7% and 81.7% for methoxy, ethoxy and butoxy biodiesel, respectively. The cloud point for methyl and ethyl biodiesel increased slightly, while a reduction of 1 K was achieved for butyl biodiesel. The presence of by-products negated much of the expected improvement in cloud point for butoxy butyl biodiesel. Further optimisation work is required to improve both conversion and selectivity if significant improvements in cloud point are to be achieved. (C) 2008 Elsevier Ltd. All rights reserved.