What Is TBN In Engine Oil?

Mechanic or petroleum engineers when faces a question again and again. That is, what is TBN in engine oil? Well, you may need to know it, as we all need to know some basics of engine oil. And one of the main basis of engine oil is TBN. 

TBN means the Total Base Number of Engine oil, which indicates the Presence of Alkaline (KOH) in mm to neutralize the acidic component of engine oil. In most cases, TBN indicates the engine oil life, which means by finding the TBN you can understand the remaining oil life of the engine oil.

So TBN is very important for engine oil. Let’s come to the Point:

what is tbn

Importance of TBN in engine oil

Total base number (TBN) is very important for engine oil because it neutralizes the acid which is produced by oxidation. Sulfur or ash contained in the fuel also creates acid which must be neutralized by TBN.So if the required TBN number is not present in the oil, the engine will face different difficulties like engine failure, low service time, or piston deposit. Actually, the main thing is that due to lack of TBN your engine oil life will fall dramatically.

What Is TBN in Engine Oil

What is TBN & TAN of oil?

TBN & TAN are both important parameters of engine oil. Day by day after TBN decrease and TAN increase. Actually, TBN is used to control the TAN and other acidic compounds of the oil. here TAN means the Total Acid number of oil. Diesel & Marine engine oil is formulated with high TBN like 10-12, on the other hand, Gasonile oil does not need a high TBN. Mainly higher TBN number is depleted for oxidation and for the acidic sulfur content of the fuel. That’s why the selection of good quality fuel is very important. Otherwise, your Oil TBN will be depleted and the oil drain interval will decrease.

General Queries

How to optimize oil drain by stopping TBN depletion?

You can control the falling of TBN in engine oil. As day by day TBN will decrease, on the other hand, oil life will decrease. So you have to change the oil or optimize drain interval by manipulating TBN depletion. For this, you have to sweeten in engine oil.

What is Sweetening in Engine oil?

This is the process of making engine oil life better by adding additives or adding some new oil by replacing some old quantity. In this way, first, you have to make a calculation of the TBN depletion rate & how much TBN you have to increase for Oil life sustain. You use different kinds of apps or software like the TBN simulator for this.

why do marine engines need high tbn oil?

HFO is used in marine engines as fuel in general cases, which is high sulfur-containing oil. To protect the engine from sulfur and other acidic contamination higher TBN engine oil is used in the marine engines so that all acidic particles can be neutralized by Base. That’s why marine engine oil is always higher TBN Oil.

Final Word:

Finally, as oil exports, we will suggest you choose to optimize TBN-contained engine oil. And if you sweeten your old oil by adding fresh oil, be careful about TBN, so that doesn’t too much high or too much lower than the engine OEM requirement limit.


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Emon is Lubricants specialist who studied on Petroleum Engineering in UAE. He have more than 10 years experience on different kinds of lubrication including automobile troubleshooting.