This article studies the capacity of biofuels to reduce motor fuel price fluctuations. We hypothesize the dependence between crude oil and biodiesel blend prices in Spain and the EU. Copula models are a method of study. Results suggest that the practice of blending biodiesel with diesel can protect consumers against extreme crude oil price increases. This can also help reduce the carbon emissions and the Green House Gases (GHG's) emitted upon burning fossil fuels