Techenomics, which focuses on Total Fluid Management Services, has prepared the following advice pertaining to how much TBN your oil should contain.

TBN is the Total Base Number, which is a measured level of base reserve built into the additive package, known as reserve alkalinity. Reserve alkalinity is measured in milligrams of potassium hydroxide per gram (reported as mg KOH/g) and is designed to neutralize harmful acids that are produced during the engine combustion process. The higher the TBN value, the more reserve alkalinity or acid neutralizing ability the oil contains. The alkalinity compounds are used to fight against organic, sulphurous and sulphuric acids formed in the oil.

There are advantages and are also disadvantages of using a high based TBN oil (known as High Overbased Sulphonates) and it’s not just because the price is much higher. High TBN oils can produce high ash content that can impair engine efficiency and cause loss of power, which will lead to excessive deposit build-up on pistons and valves. High ash is caused by non-combustible residue of an oil’s detergent additives, these additives contain derivatives such as barium, calcium and magnesium.

These deposits can lead to the following devastating results:

  • Ash deposit build-up on pistons and valves
  • Loss of oil stability
  • Polishing of cylinder line bores
  • Valve guttering
  • Loss of power
  • Increased oil consumption
  • Increased fuel consumption

To understand TBN and figure out how much TBN is needed in oil, we first need to have some knowledge of the sulphur content contained in diesel fuel. Sulphur content varies from one country to another.

In Australia the government legislation requires diesel fuel at the bowser to have a maximum sulphur content (ULSD-Ultra Low Sulphur Diesel) of 10ppm (10mg/kg). You need to know the sulphur content to determine what TBN concentration level is needed in engine oil.

TBN values for Direct Injection (DI) engines are generally calculated to be 10x the sulphur content and for a Precombustion Chamber (PC) Engine, they are calculated at 20x the sulphur content. However, when the sulphur exceeds 1.5%, then consider using an EOM Recommend specifications to maintain adequate wear protection.

It is considered to be abnormal when the TBN deteriorates to 50% of the new oil TBN value. Meaning the oil needed to be changed because it has lost the ability to neutralize acids. With increased emission controls, sulphur diesel fuels are now very low (ULSD), TBN values reflect these changes by having a new TBN value of generally around 8 or 9 mg KOH/g.


  • High TBN oils do not necessarily mean that the oil is better than that of a lower TBN oil. A high TBN oil has greater capabilities of counteracting acids.
  • Unnecessary high TBN oils can produce ash build-up that will cause sequential effects to your engine.
  • Consider using an OEM recommended oil specification to ensure adequate wear protection.


  • Find out the sulphur content in your diesel fuel
  • Have your oil analysed, and
  • Check OEM recommendations.

From this information, you can make clear decision on which oil is best suited for your engine’s performance and well-being.

Contact Techenomics if you are still unclear on how much TBN your oil should contain. To enquire about TBN please contact Jason Davis, email: [email protected] or visit

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