New generation bio-fuels, ultra low sulfur fuels, and mineral fuels require assessment of thermal and storage stability. Their hydroprocessing and usage can form hydroperoxides which reduce thermal stability, particularly as biofuels lack natural antioxidants. A range of secondary oxidation products (alcohols, ketones, acids) may form during engine operation, particularly for jet fuels under high thermal stress. Trace oxygen product measurement is demanding and imprecise. This project will develop new multidimensional and hybrid gas chromatography and mass spectrometry methods to provide accurate quantification and identification of all oxygenates, chemical precursors and synthesis routes, and will propose methods to alleviate oxidation.