1. Essences

At service stations, particularly in France, motorists are offered several types of petrol; these generally have similar physical properties, but differ in their octane ratings or in their level of "finish", which leads to particular formulations (bases, additives) distributed under specific trade names (since 2006: V-Power, Ultimate, Excellium, for example). In what follows, we will focus on the characteristics of conventional unleaded fuel, known as SP 95 or Eurosuper, which is widely distributed in Europe under EN228 specifications.