TBN Analizi — ASTM D2896 / ASTM D4739 / ISO 3771

What Is TBN?

Total base number (TBN) is a measure of the oil's ability to neutralize acids and is expressed in mg KOH equivalent to one gram of sample. The sample is dissolved in the appropriate solvent and titrated with acid. Two common methods use different acids and give different results on the same sample.

Purpose of TBN

The aim is to determine how much of the engine oil retains its capacity to neutralize the acids formed during combustion. When TBN is depleted, corrosive wear begins.

Which Products Is TBN Applied To?

Passenger and heavy vehicle engine oils
marine cylinder oils
Gas engine oils
Generator engine oils
Oils of engines using high sulfur fuel

In Which Sectors Is TBN Used?

Oil & GasPetrokimyaEnergyAutomotiveMaritimeEnergy

Standards Related to TBN

ASTM D2896 (perklorik asitle potansiyometrik titrasyon)
ASTM D4739 (hidroklorik asitle potansiyometrik titrasyon)
TS ISO 3771 (perchloric acid method)
TS ISO 6618 (color indicator method)

TBN Conditions

Method difference: D2896 and D4739 results are different in the same sample and should not be confused
Reference: The TBN value of new oil is required for comparison
fuel sulfur: High sulfur fuel accelerates TBN consumption
Unit: mg KOH/g

Equipment for TBN

Automatic potentiometric titrator
Analytical balance
Titration electrodes
magnetic stirrer

Sample Requirements for TBN

A clean sample container should be used
New oil TBN value must be ensured
Fuel sulfur content and engine type must be declared
Service period and amount of reinforcement, if any, should be specified.

Duration of TBN

Titration is rapid; The results are usually obtained the same day or the next day.

TBN Procedure

1The sample is weighed and dissolved in the solvent.
2It is transferred to the titration cell.
3Electrodes are placed.
4Titrate with standard acid solution.
5The turning point is determined.
6TBN is calculated as mg KOH/g.

TBN Acceptance Criteria

There is no fixed universal limit; The evaluation is made based on the new oil value. Engine and oil manufacturers may define a decrease of the TBN to a certain percentage of the new oil value as the threshold for oil change; In marine cylinder oils, TBN class is selected according to fuel sulfur.

Evaluation of Results

The difference between the two methods is significant: D2896 also counts weakly basic compounds and generally gives a higher result. It is imperative to maintain the same method of monitoring used oil; If the method is changed, the trend will be misleading. The rate of TBN decline is directly related to fuel sulfur and combustion efficiency.

TBN Report

Oil type, engine information and service period
Standard and method applied
TBN sonucu (mg KOH/g)
New oil reference value and remaining percentage
Fuel sulfur content
Trend assessment

Accreditation

EUROLAB holds internationally recognised accreditation obtained from accreditation bodies party to the IAF and ILAC multilateral recognition arrangements, under ISO/IEC 17025 for laboratory testing, ISO/IEC 17020 for inspection and surveillance, and ISO/IEC 17021-1 and ISO/IEC 17065 for system and product certification. This chain ensures the reports and certificates issued are accepted worldwide.

Whether this test can be offered within accredited scope depends on your product and the standard applied; since accreditation is method-based, the scope is confirmed in writing at the quotation stage.

Scope and authorisations

Related Regulations

Fuel and LPG market technical regulations (EPDK)
EU 2009/30/EC (fuel quality directive)
Communiqués on the placing of lubricating oils on the market

Petroleum, Fuel and Oil Analysis — What Does This Testing Field Cover?

The section below describes the field that the TBN test belongs to; the conditions and acceptance criteria of this particular test are given in the sections above. The scope specific to your product is confirmed in writing at the quotation stage.

Petroleum, fuel and oil analysis determines whether a fluid meets its specification and how it behaves in use. Standards in this field consist largely of ASTM and EN publications, with a separate method defined for each parameter.

What distinguishes this family is that product specifications are written as PARAMETER LISTS. Specifications such as EN 590 (diesel), EN 228 (petrol), EN 14214 (biodiesel) and ISO 8217 (marine fuels) state for each parameter both the limit and the method by which that limit is to be measured. If the method changes the result may change too; the specification therefore binds the method as well, and the use of an "equivalent method" is possible only where the specification allows it.

On the fuel side, parameters describe three different properties of the product. Physical properties (density, viscosity, distillation curve, pour point, cloud point) determine pumpability and cold weather behaviour. Combustion properties (cetane number, octane number, calorific value) indicate performance in the engine. Contaminant and stability parameters (sulphur, water, sediment, oxidation stability, copper strip corrosion) affect both emissions and storage life.

Oil analysis is carried out for two different purposes and the two must not be confused. Analysis of NEW oil verifies the conformity of the product to its specification: viscosity index, additive content, flash point. Analysis of USED oil, by contrast, is done to read the condition of the machine — elemental analysis shows wear metals (iron, copper, chromium, aluminium), water and fuel contamination point to leaks, and oxidation and acid number determine the remaining life of the oil.

Used oil analysis is therefore a PREDICTIVE MAINTENANCE tool. The trend of samples taken at regular intervals is followed; it is the trend rather than a single result that is meaningful. Iron levels climbing over the course of months allow intervention before a failure occurs.

Marine fuels are the most active sub-body of the field. The global tightening of sulphur limits has brought new blended fuels onto the market; for these fuels stability, compatibility (whether two fuels form deposits when mixed) and catalytic fines content have become critical parameters.

Sampling is part of the result in this family too. A sample taken from the bottom of a tank shows different water and sediment content from one taken from the upper level; in commercial deliveries the sampling point and method are set by contract.

Method groups in this field

Physical properties
Density (oscillating U-tube and hydrometer), kinematic viscosity, distillation, pour and cloud point, flash point.
Combustion properties
Cetane number and cetane index, research and motor octane number, calorific value.
Sulphur and elements
Sulphur by UV fluorescence and XRF; elemental analysis and additive content by ICP.
Stability and corrosion
Oxidation stability, copper strip corrosion, water and sediment, filter blocking tendency.
Composition analysis
Boiling range distribution by gas chromatography, hydrocarbon types (FIA), benzene and aromatics content, fatty acid methyl ester content.
Used oil
Wear metals, contamination (water, fuel, soot), oxidation, acid and base number, change in viscosity.

Commonly confused in this field

The specification binds the method as well; a result measured by a different method may not be accepted for specification conformity.
A single result on used oil is not meaningful; the decision is made on the trend.
The sampling point determines the result; the tank bottom and the upper level show different water and sediment.
The cetane index is a calculated value and is not the same thing as a measured cetane number.
Fuels blended with biodiesel behave differently in terms of storage life and microbial growth; classical diesel parameters are not sufficient.
Mixing marine fuels from different sources can cause deposits; compatibility is assessed separately.

Which decisions these results support

Conformity of a fuel lot to specification and commercial delivery
Predictive maintenance decisions based on used oil analysis
Determining parameters for customs and tax classification
Quality verification after storage, blending and transport
Compliance with sulphur limits under emissions legislation

Related Tests

Frequently Asked Questions About TBN

We received different TBN from two different laboratories, why?

Most likely different methods were used. ASTM D2896 and D4739 give different results on the same sample, and this is not an error. The same method must be used for comparison.

TBN fell but TAN did not rise, is there a problem?

TBN decline is an expected consumption; The real warning sign is when TAN starts to rise. When the two approach intersection, it indicates that the oil's neutralizing capacity has been exhausted.