Benzoxazinone 2 was prepared and reacted with formamide, acetamide, some primary aromatic amines and heterocyclic amines giving the corresponding quinazolone derivatives 3-15 respectively. The reaction of benzoxazinone 2 with hydrazine hydrate and phenyl hydrazine was also studied. Representative compounds of the synthesized products were evaluated as antioxidants and corrosion inhibitors for gasoline engine lubricating oil. The highest antioxidant activities were obtained with compounds 10-15. The optimum concentration recommended for these new additives was found to be 0.1g for 1L of oil for compounds 13-15. In addition, some of the highly effective antioxidant additives, namely 10-15, were thermally analyzed by using thermogravimetric analysis (TGA) and differential thermal gravimetric analysis (DTGA) techniques and the results indicated that compounds are thermally stable and could be used under thermal conditions. Moreover, a comparison of the oxidation stability between the tested oil containing the prepared products and lubricating oil containing commercial additives was also studied.