Depending on Si content, minor element such as Sr was used with hypoeutectic and P for hypereutectic Al-Si to modify the solidified microstructure leading to performance improvement of cast aluminum alloys. Due to economic and recycling, there is need for a universal modifier that can be used in larger range of Si content. Previously, microstructure modification and ductility enhancement was obtain in nearly eutectic, A4047, alloy when treated with nano-structured chemical based on triphenyl silanol polyhedral silsequioxane (TSP). It was postulated that silanols react with the active aluminum surface to form stable Si-O-Al bonds, while cage-like silsesquioxane core controls the subsequent solidification process. Similar approach was used in hypoeutectic (A319) and hypereutectic (A391) casting alloys. Using standard casting approach, highly refined proeutectic aluminum in A319 and proeutectic silicon in A391 was observed, which lead to improve ductility and wear resistance, while maintain their tensile strength, respectively.