TBN stands for Total Base Number and is expressed in mg KOH/g. It indicates how much alkaline material is present in the oil to neutralise acidic combustion products. This is particularly important in diesel engines and engines running on fuels with a high sulphur content. During combustion of sulphur-containing fuel, sulphuric acids are formed, which can be harmful to the engine if not neutralised.
A higher TBN means the oil is capable of neutralising acids for a longer time, which helps prevent engine damage and may extend oil drain intervals. However, TBN is not a direct measure of an oil’s cleaning performance.
Cleaning vs. neutralising: what determines cleaning performance?
Although TBN indirectly reflects the presence of detergents (cleaning additives that dissolve contaminants), the actual cleaning power of an oil mainly comes from the additive package: detergents and dispersants. Dispersants encapsulate microscopic dirt particles to keep them suspended in the oil, preventing deposits. So, an oil with a lower TBN can still deliver excellent cleaning performance—provided the additive system is well-formulated.
Both are important, but they serve different purposes.
In which situations is a high TBN desirable?
A higher TBN is especially important in markets or applications where fuel quality is poor. Think of aged diesel or diesel with a high sulphur content. In addition, there are other situations where a high TBN is essential:
Diesel with high sulphur content
Marine vessels and large two-stroke engines
Off-road, agricultural, and developing regions
Landfill gas, biogas, and sewage gas engines
Extended drain intervals
Heavy-duty EGR diesels and high soot loading
Regions where a high TBN (>10–12) is recommended:
Sub-Saharan Africa: Many diesel fuels contain >500 ppm sulphur, sometimes up to 2000 ppm.
South and Southeast Asia: In countries such as India, Indonesia, Myanmar, and Bangladesh, locally refined fuel of varying purity is still used.
South America: In Bolivia, Peru, and Paraguay, fuel quality is not consistently uniform.
Middle East and North Africa: Sulphur-rich fuel is still in use in Yemen, Iraq, and parts of North Africa.
Central Asia and parts of Eastern Europe: In Kazakhstan, Ukraine, and Uzbekistan, off-road applications often involve diesel of varying quality.
In all these regions, a high TBN oil extends engine life and helps prevent corrosion damage.
Fuel quality in Europe: when is TBN enhancement necessary?
In Western Europe, fuel quality is generally excellent (ULSD <10 ppm sulphur), which means low SAPS oils with a lower TBN (6–8) are usually sufficient. However, in Eastern and Southern Europe, there may be regional differences. This is particularly relevant for holidaymakers travelling by car or camper through these countries, or for freight traffic headed toward the Middle East.
Country
Fuel quality
TBN booster needed?
Slovakia
Good (<10 ppm sulphur)
No
Hungary
Good
No
Croatia
Good to fair
Usually not
Romania
Good to variable
Only under heavy load
Bulgaria
Good to variable
Only for specific applications
Greece
Good, islands vary
Possibly for off-road or camper use
Serbia
Variable, up to 500 ppm sulphur
Yes, especially outside cities
Turkey
West: good, East: variable
Yes, in eastern and border regions
When driving for long periods with campers, off-road vehicles or agricultural equipment in remote areas, a higher TBN oil may be advisable—even within Europe.
Striking the right balance between protection and system compatibility is essential. In many modern engines, a lower TBN is preferred, but in challenging environments, a high TBN remains crucial for reliable performance.
