Patent ID: 7299682

Claim:
A method for determining the total base number of a used lubricant from an open, all-loss, lubricating system comprising: a) applying an AC voltage signal between electrodes immersed in the used lubricant, b) measuring the used lubricant dependent response to the applied signal, and c) determining the used lubricant base number from the measured response; wherein the method further includes the steps of at least one of the following selected from the group consisting of: i) receiving input of the total impedance or impedance equivalent of the fresh lubricant, ii) receiving input of the TBN or TBN equivalent of the fresh lubricant, iii) applying a second AC voltage signal between electrodes immersed in the fresh lubricant and measuring the fresh lubricant dependent response to the applied second signal, and combinations there of, for use in determining the used lubricant's base number.