A new check, TBN (total base number), has recently been added to the battery of tests Pon routinely carries out on lubricating oil under the name ‘systematic oil sampling’ or S.O.S. This important new indicator measures the oil’s ability to neutralize acids.

The internal combustion process in an engine generates acids. If the oil is no longer able to neutralize these acids, they will attack the engine and speed up wear. The acidification level of the oil is considered to be too high if the TBN falls to half the value for fresh oil. For example, CAT DEO 15W40 lubricating oil has a TBN value of 10.6 mg KOH/g when new. When the TBN falls to half this value, i.e. 5.3 mg KOH/g, it is time to change the oil.

You can find the TBN reading in the TBN column of the S∙O∙S report for your engine, which can also be accessed by visiting the website www.sos-online.nl.