Total base number

Total Base Number (TBN) is a measurement of basicity that is expressed in terms of the equivalent number of milligrams of potassium hydroxide per gram of oil sample (mg KOH/g) that is required to titrate and neutralise the acidic components in a sample. TBN is an important measurement in petroleum products, and the value varies depending on its application. TBN generally ranges from 6–80 mg KOH/g in modern lubricants, 7–10 mg KOH/g for general automotive use and 10–15 mg KOH/g for diesel operations. TBN is typically higher for marine grade lubricants, approximately 15-80mgKOH/g, as the higher TBN values are designed to increase the operating period under harsh operating conditions, before the lubricant requires replacement. Basic additives are introduced into the oil formulation, which can react and neutralise acids in fresh and used oil formulations [2]. Therefore, it prevents damage of engine parts, which includes corrosion of metal surfaces and damage to gaskets and other seals in an engine, by acidic components in the oil. The constituents that may be considered to have basic characteristics include organic and inorganic bases, amino compounds, salts of weak acids (soaps), basic salts of polyacidic bases, and salts of heavy metals. [2]. Weak organic and strong inorganic acids are formed by oxidation of the lubricant or from the combustion of trace impurities such as sulphur. The TBN value of oil will gradually drop over time as an engine is operated, so routine testing for TBN can provide useful information about serviceability of the oil and an early warning of developing corrosion problems [3]. TBN can also be a particularly useful tool in assessing the combustion efficiency of an engine, if rapid depletion is observed [4] . Fuels containing a higher amount of impurities such as sulphur have a greater potential of forming sulphuric acid, which would decrease the TBN sooner [2].