TBN depletion

Lubricant Consumption Trending

Medium speed engine development over the last two decades resulted in extreme reduction of lubricant consumption down by 90%. This decrease in consumption on heavy fuel operated engines, in combination with the increase in engine load is leading towards a continuous increasing stress on the lubricant, resulting in severe TBN (Total Base Number) depletion and viscosity increase due to fuel contamination.

During the last 15 years lubricant manufacturers introduced TBN 50 medium speed engine oils to deal with these trends. However for a TBN 50 oil in combination with higher than 1% Sulphur fuels, the modern engine oil consumption is insufficient to create an acceptable TBN equilibrium, resulting in the need for partial or full sump replacement.

TBN Depletion

The TBN (Total Base Number) of a lubricant is a measure for the capabillity of a lubricant to neutralize sulphuric acid formed during the combustion process.
During this neutralization of sulphuric acid the TBN additive is consumed creating TBN depletion. The TBN additive is replenished by the added fresh lubricant. The majority of TBN additives used is a Calcium based additive technology transfering the sulphuric acid to a harmless Calcium Sulfate. It is not possible to add a separate TBN additive to the lubricant in service as this would increase the total amount of Calcium in the lubricant disturbing the sensitive balance in the lubricants formulation.