Patent ID: 7172903

Claim:
A method for monitoring oil aging and particulate buildup in a lubricant, other than one exposed to combustion products, comprising: detecting, on-line and in real-time, light of two or more preselected wavelengths transmitted through the lubricant, at least one wavelength being in the visible or near infra-red spectrum, wherein the wavelength of the visible or near infra-red spectrum is from about 400 nm to about 850 nm, and one other wavelength being in the near infrared spectrum, wherein the wavelength of the near infra-red spectrum is from about 875 nm to about 1100 nm, the light being transmitted over a pathlength of greater than or equal to 0.5 cm; and comparing light detected with a predetermined value for each wavelength whereby oil aging and particulate buildup is monitored.