Biodiesel degradation rate after refueling

► No autocatalytic effects from oxidation products after refueling were detected. ► Degradation products left in the tank before the refill will be diluted. ► Degradation products are proportional to the average age of the fuel. The overall objective of this study was to firmly investigate if the refueling frequency influences the degradation rate of biodiesel and find out if primary and secondary oxidation products can act as initiators for biodiesel degradation in absence of metals. Duplicate samples of B7 Reference fuel Euro VI and B100 methyl rape seed ester were studied during accelerated aging in an open to dry atmosphere system at an elevated temperature (80°C) during 14 days. Determinations of water, short chain fatty acids as well as structural changes using infrared spectroscopy were used as degradation measures during aging and complemented with total acid number and hydroperoxide concentration at the end of the experiment. The study clearly shows that there are no autocatalytic effects from left over fuel after refueling and thus, the primary and secondary products do not directly influence the degradation rate of the fuel and that the fuel quality are in fact improved after refueling as the remaining degradation products are diluted.