This document released by Wilhelmsen describes the fuel oil and lube oil test methods. The Total Base Number is determined by measuring the pressure build-up in the cell when a pre-determined quantity of oil sample is added to a special reagent. Then, we determine the amount of sample needed by the cell measurement processor; this amount is based on the expected TBN. When using this instrument for the very first time it is necessary to calibrate it for each of the oil grades to be measured. The cell is able to hold calibration data for up to seven different oil grades. The calibration process requires a sample of new oil for each of the grades to be measured. We recommend you use the oil grade name as the "Name" during the cell setup process. The cell should be re-calibrated approximately every six months. The calibration can be checked by using new oil in the TBN test procedure, in place of used oil. The'test'TBN should be close to the new oil TBN.