Free fatty acid numbers are often used as arbitrary measures of fuel quality. An increase in fatty acids should thus correlate with fuel degradation, such as polymerization that restricts fuel flow. I plan to evaluate the environmental conditions the fuel encounters in storage and during engine use to characterize fluctuations in biodiesel properties. Such information can help predict the performance and shelf life of biodiesel fuel and give insight into improving and promoting biodiesel fuel as a viable alternative fuel.