A systematic study of MFI-like zeolites synthesis starting from template-free reaction gels was carried out. It was possible to prepare either MFI- or MOR-like zeolites from the same synthesis gel by only changing either temperature or crystallisation time. An upper limit for the incorporation of silica in the MFI framework was observed regardless of the silica-to-alumina ratio of the starting gel, the resulting solids having Si/Al ratios ranging from 12 to 29. A good Linear correlation between the corrected rate for n-hexane cracking and the Al loading confirmed the composition and purity of the zeolitic MFI-phase obtained. Hydrothermal treatments applied to two MFI zeolites with different Si/Al ratio caused a higher percentage of dealumination for the one containing the highest Al loading, but the number of Al atoms per unit cell remaining after severe (1023 K) steaming was the same (1.4+/-0.35) in both cases. Enhancement of the catalytic activity for n-hexane cracking was observed for the samples steamed under mild (873 K) conditions with this effect being more pronounced for the aluminium-rich zeolite. Treatments of the sample showing the highest activity enhancement with HCl solutions of increasing concentration caused a progressive removal of extraframework Al species (EFAL) with a concomitant decrease in the catalytic activity. However, only a partial extraction of EFAL was observed, even with the more concentrated acid solution, suggesting a strong interaction of these species with the zeolite framework.