In this paper, the effect of adding silica nanoparticles on the high- and room-temperature mechanical properties of the piston aluminum alloy is investigated. Aluminum alloy samples were fabricated by gravity-casting in the cast iron mold. However, nano-composite specimens were produced by stir-casting and with the addition of 1% of nano-SiO2-partiles to the melt. Due to the working conditions of the engine piston at high temperatures, tensile tests were performed at temperatures of 25, 250, 275 and 300°C and at a rate of 1 mm/min. After the tests, the sensitivity analysis was performed on the test results using the Minitab software. The experimental results showed that for all samples, the temperature increase had an effect on the yield stress, the ultimate tensile strength and the fracture strain. In aluminum alloy samples, increasing the temperature led to decrease in the yield stress and the ultimate tensile strength and the fracture strain increased. For nano-composite specimens, increasing the temperature enhanced the fracture strain and decreased the yield stress and the ultimate tensile strength. In general, mechanical properties of the nano-composite improved compared to the aluminum alloy. Therefore, the elastic module at 25°C increased as 23% and the elongation at this temperature decreased as 18%. These improvements at 300°C was the increase of 58% and the decrease of 25%. The improvement in the yield stress was 4% and 9% at 25 and 300°C respectively, by adding nano-particles.