In the industrial sector and in the research and development of new chemical-industrial technologies, the term nanofluids has been used for only a few decades. Intensive nanofluid research has proven to be extremely productive and it continues to reveal new features of these systems that build on current technology. Research is mainly focused on cooling systems due to the increased thermal conductivity characterized by nanofluids, but recently attention has been focused on the use of nanofluids in ballistic protection. The systems currently being investigated as effective ballistic protection systems are based on polyethylene glycol (PEG) and attempts are being made to find more economically viable alternatives. The aim of this work was the preparation and characterization of nanofluids whose base fluid were polyalphaolefin oils of different viscosities and different compositions (PAO4, PAO6, PAO8), and the filler were SiO2 nanoparticles. Nanofluids were prepared 0.5; 1.0; 2.5; 5.0; 7.5 and 10 wt. % SiO2. The influence of base fluid types and concetration of nanoparticles on thermal conductivity, electrical conductivity, stability and rheological properties of prepared nanofluids were investigated. The study showed that the prepared nanofluids were Newtonian fluids with low dielectric constants. Thermal conductivity testing showed that the addition of nanoparticles to the base fluid increases the thermal conductivity of nanofluids. As the temperature increases and the SiO2 concentration in nanofluid decreases, the viscosity decreases. Prepared nanofluids showed that they are relatively stable systems, while the highest stability was recorded for nanofluids with a base fluid of the highest viscosity, PAO8.