A device (1) for treating liquid fuel, comprising at least a pair of permanent magnets (7) having a same polarity and defining between them a liquid fuel treatment area (T) arranged at a distance of not more than 80 cm from a combustion chamber. The magnets (7) are induced by a magnetic flux of between 15000 and 20000 gauss, they have a heat resistance of at least 1300C, are arranged at a distance of between 4 and 8 mm from one another and are at least 6 cm long.
