Base Number (BN)

Motor oils are constantly exposed to acidic combustion products during operation, which leads to a reduction in the alkaline reserve of the oil.

Alkaline reserve

The alkaline reserves of the engine oil are used up during the operation of engines.


Without a base balance, acids from the combustion process can attack the materials.


CMT has made 3 different versions of the test cell to combine the functions for a usecase.

The CMT BN Test Kit provides state-of-the-art analysis and gives fast, accurate results within a couple of minutes.

The Standard BN Test Kit has been developed for all standard applications like testing the system oil used in all kinds of diesel engines, while the CDO BN Test Kit has been specially developed to test the scraped down cylinder drain oil in two stroke crosshead engines.

The CDO BN Test Kit software has been developed specifically to give reliable results despite the fact that used drain oil may have dropped down to only 10% BN reserve left compared to the fresh oil.

The CMT BoB BN Test Kit allows to test the base number of cylinder oils blended on board. It will report the BN of the blend as well as the mixing ratio. Furthermore the BoB BN Cell allows to test the remaining BN of the drain oil and the remaining BN of the system oil. For easier handling it allows to store calibration for 5 different system oils and 3 different cylinder oils for drain oil testing.

Following Test Kits are available:

Standart BN - for system oil only
CDO BN        - for cylinder drain oil only
BoB BN         - for system oil, cylinder drain oil and blending


Product info

Related articles

Your Benefits

  • Protect your engine from acidic residue of the combustion process
  • Quick measurement
  • Easy test with intuitive software
  • Save measurements for trend analysis

Ordering Information


Standard BN Test Kit (for system oil)
Range: 1-180 BN
Accuracy: Typically +/- 5 % of fresh oil BN

CDO BN Test Kit (for cylinder drain oil)
Range: 1-180 BN
Accuracy: Typically +/- 5 % of fresh oil BN

BoB BN Test Kit
(for blending, cylinder drain oil)
Range: 1-500 BN
Accuracy: Typically +/- 2% or +/- 3 of
fresh oil BN

Dimensions: Ø 68 mm x 84 mm
Weight: 490 g
Test Time: 5 minutes
Memory: last 10 readings for each
individual oil
Reagents: non hazardouz

Reagent & Spares

Spare BN TouchCell

Spare CDO BN TouchCell

Spare BOB BN TouchCell

Set of O-Rings for TouchCell

Download Option TouchCell License for Datadownload