Application of new materials allows to offer more sensitive, selective and long term stable sensors, as well as to employ its modification possibilities for gas sensor efficiency improvement. The aim of the present work is to compare gas response to acetone of nanostructured sol-gel auto-combustion synthesis derived stoichiometric and excess-iron cubic spinel type nickel zinc ferrite with formula Ni0.3Zn0.7Fe2+zO4 (where z = 0 and 0,1) is compared. Detailed synthesis steps and gas sensing measurement methodology were described. The sensor material was characterized by x-ray diffraction, scanning electron microscopy and direct current resistance measurements. X-ray diffraction analysis confirms that samples formed the single phased cubic spinel structure and no peaks from impurity phases were detected. The scanning electron microscopy reveals nanosized grains less than 100 nm in diameter. Plots of resistance versus temperature show adsorbed water contribution to the conductance. Overall, sensors were tested at temperature interval from 150 oC to 325 oC in order to identify operating temperature of the material. The response-recovery characteristics also were performed. It was found, that with excess-iron in the Ni-Zn ferrite, changes its DC electrical resistivity, type of conductivity, as well as response to reducing gas (more than 2 times) and operating temperature. Obtained relationships can be explained with Fe2+ formation in the material, thus increasing charge carrier (electron) concentration. This leads down to higher oxygen adsorption ability which can act with test gas. Overall performed study reveals alternative way how to enhance sensitivity of spinel type ferrite gas sensor materials avoiding synthesis of complicated nanostructures or precious metal doping.