5.1 Lubricants can contain basic constituents that are present as additives. The relative amount of these materials can be determined by titration with acids. The base number is a measurement of the amount of basic substances in the oil under the conditions of the testing procedure.

5.2 A primary objective of a marine cylinder lubricant is the neutralization of sulfuric acid, produced during fuel combustion, to protect the engine from corrosion. The EBas method characterizes the more efficient basic species of the lubricant reacting with acids from the beginning of the neutralization (when the lubricant milieu is basic) until an equilibrium state where the lubricant becomes slightly acidic. The use of hydrochloric acid (HCl) allows differentiating basicities of various strengths during titration.

5.3 In marine lubricants, the constituents that can be considered to have basic properties are primarily organic and inorganic bases coming from the detergent. Basicity can also be brought to the lubricant by other components including dispersants, amino compounds, or any organic basic components. This test method uses the same titration system as that of Test Method D4739, however the evaluation and interpretation of the titration result is different. The hydrochloric acid is used as the titrant in this test method and Test Method D4739, whereas Test Method D2896 uses a stronger acid, perchloric acid. While all three methods can be considered as complementary to evaluate the basicity of lubricants, this test method is only used for marine cylinder lubricants.

5.4 This test method measures only the efficient basicity of the lubricant, which represents only the part of the total basicity, until the point of which the lubricant becomes slightly acidic. It will depend on the components of the formulation itself. In that respect, the EBas cannot be compared to base number given by Test Methods D4739 or D2896. The EBas is then complementary information to the base number, giving performance in efficiency of neutralization of acidic species.