Patent ID: 7839492

Claim:
A method of detecting fuel in oil comprising: a. providing an excitation light source for exposing an oil sample to light in order to excite the oil sample from a non-excited state to an excited state, and a spectrally selective device for detecting light emitted from the oil sample as the oil sample returns from the excited state to a non-excited state; b. operating said excitation light source to expose the oil sample to excitation light in order to excite the oil sample from a non-excited state to an excited state; c. operating said spectrally selective device to detect a fluorescent light signal emitted from the oil sample as the oil sample returns from the excited state to a non-excited state to produce spectral indicia; and d. ascertaining the concentration of fuel in the oil sample by comparing a ratio of a fluorescent light signal in two or more spectral regions and/or by comparing a spectral signature of a fluorescent light signal in two or more spectral regions.