Lube Notes: Motor Oil Formulation - 2

Volume 1 Issue 2 - Lubrication

Article Index
Lube Notes: Motor Oil Formulation
Total Base Number
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Total Base Number

Total Base Number (TBN) refers to an oil’s ability to neutralize acid. TBN is measured on a scale of one to 13: the higher the number the greater the capacity to neutralize acids. A high TBN is required for extended drain interval oils and most diesel oils should have a TBN between eight and 12.


The combustion process by-products form sludge and varnish deposits in the engine. Deposits can cause hot spots in the engine, affecting its performance and fuel economy. Detergents are added to aid in removing these deposits.


Combustion by-products, such as carbon, are maintained in solution by dispersants, reducing deposits. Dispersants are designed to keep the by-products in the oil until the filtration system can remove them. Dispersants and Detergents work hand in hand to keep the engine clean.



Imagine a blender whipping your motor oil and you will get a pretty good picture of how the oil is whipped by the rapidly moving parts in the engine. As the oil is whipped, it traps air. The resulting foam has very poor lubricating properties. Chemical additives such as silicone are added in near trace amounts to reduce foaming. The effect of these anti-foaming additives is to weaken the air bubbles, allowing them to collapse more quickly, thus reducing the amount of foaming that occurs.



Seals come in various sizes, shapes and materials. It is necessary for motor oils to not only be compatible with the materials, but to nourish the seals. Seals should not degrade, dissolve, crack or shrink. As an additional benefit, some, but certainly not all, oils even cause a little swelling of the seal.

Motor oil is certainly more than just refined crude in a bottle; it is a marvelous product that is the result of years of research and millions of hours of use. Motor oils have improved constantly from the days of whale oil and animal fats so that today’s oils accomplish multiple tasks and not merely lubrication. In my next edition of Lube Notes, I will look at API and SAE classifications.

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