Oil Analysis - TBN & TAN

The TAN test is usually performed in relation to two methods, IP139 and IP177 and can determine if any acidic compounds are forming within the machine, which will reduce the life and quality of the lubricating oil.

TBN

The TBN test determines the amount of reserve alkalinity present in the lubricant. This reserve alkalinity is part of additive packages found in engine oils and its function is to protect the crankcase from the corrosive acidic components produced in the combustion chamber.

Diesel fuel contains sulphur; this burns and forms SO2 and SO3 in the combustion chamber of the engine. Diesel also burns to produce CO2 and water, while the Nitrogen from the air produces Nitrogen Oxides (NOX) compounds. The water and Sulphur Oxides mix to form Sulphuric acid, and the Nitrogen Oxides combine with the water to form Nitric acids.

This acid mixture would destroy engine parts rapidly. Therefore it is essential to remove these acids as quickly as possible. This is done by introducing an alkali solution into the oil to neutralise the acids before they attack the engine. All unused oils will have a reference TBN value: it is the change in this value from the unused, which measures the reserve alkalinity remaining in the lubricant.

The TBN value is obtained by titrating the engine oils with acids and the results are expressed as mg/KOH/g.

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