Abstract: A method of determining the quality of oil by irradiating the oil at a first wavelength, e.g., of about 470 nm, measuring a level of fluorescence of the oil at a second wavelength, e.g., of about 520 nm, comparing the measured fluorescence level to a predetermined threshold level to determine whether or not the oil quality is acceptable. The oil is preferably discarded if the measured fluorescence level exceeds the predetermined threshold level, which can be generally dependent on the oil composition. The fluorescence is correlated to the level of polar components in the oil. Also described are devices for determining the quality of oil via fluorescence.