The present work was undertaken to study the role of the major operating parameters commonly applied in aluminium foundries, as well as the effect of minor alloying elements on inclusion formation in one of the most widely used Al-Si alloys, i.e., A356.2 primary alloy, using the porous disc filtration apparatus (PoDFA) technique. A set of 23 experiments was conducted (each using a melt of 25 kg of fresh alloy material). In each case, four to six successive PoDFA trials were executed. PoDFA samples containing the unfiltered part of the metal (about 5 mm in thickness) in contact with the PoDFA filter were polished for metallographic examination. Inclusion classification and counting were done using the grid method. The present work summarizes the types and concentrations of non-metallic inclusions as well as aluminium oxide films that can occur in this alloy prior to casting.