Method for recognising the type of fuel actually used in an internal combustion engine

A method for recognising the type of fuel actually used in an internal combustion engine (1); the recognition method includes the steps of: detecting, by means of at least one sensor, the intensity (S) of the vibrations generated by the internal combustion engine (1) within a measurement time window; determining the value of at least one synthetic index (I) by processing the intensity (S) of the vibrations generated by the internal combustion engine (1) within the measurement time window; comparing the synthetic index (I) with at least one predetermined comparison quantity (TH); and recognising the type of fuel actually used as a function of the comparison of the synthetic index (I) to the comparison quantity (TH); and forcedly altering, when detecting the intensity (S) of the vibrations, the engine control with respect to the normal standard engine control, so as to enhance the behavioural differences of the different types of fuel that can be used by the internal combustion engine (1).