A series of Fe_xNi_y/SA (SA = SiO₂-Al₂O₃) catalysts were synthesized via solvothermal assisted deposition precipitation synthesis method and explored for low-temperature hydrodeoxygenation (HDO) reaction of methyl oleate into n-alkanes and vegetable oils. A comprehensive study on the effects of increasing iron oxide loading in catalyst samples, i.e., Fe₁Ni₁/SA, Fe₃Ni₁/SA, Fe₅Ni₁/SA and Fe₇Ni₁/SA, on the crystallographic, morphological, textual and surface chemical behavioural were investigated thoroughly using various spectroscopic techniques. The study disclosed excellent surface area, high acidic strength and reducibility of Fe₁Ni₁/SA catalyst due to the lowest Fe²⁺ or FeO species. In contrast, higher iron oxide loading leads to the accumulation of Fe²⁺ ions on the surface with reduced metal acid centres and diminished surface area. The catalytic conversion as well as C17-C18 selectivity in catalytic HDO was also scrutinised with particular reference to Fe²⁺/Fe³⁺ ion ratio. The obtained superior catalytic activity and C18 selectivity of Fe₁Ni₁/SA catalyst are due to the lowest Fe²⁺/Fe³⁺ ion ratio. However, the iron oxide loading increased the Fe²⁺/Fe³⁺ ion ratio, which ultimately decreased the catalytic activity. Thus, the role of Fe²⁺ species in the deactivation of catalyst was discussed in detail to establish conversion and selectivity control in the catalytic HDO pathway.