There are two commonly accepted measurement methods:
- ASTM D2896 (GOST 30050), often used for fresh oils,
- ASTM D4739 (GOST 11362), which is often applied to measure the reserve alkalinity of used oils.
There are two schools of thought about the validity of:
- ASTM D2896, which employs perchloric acid as the reagent,
- ASTM D4739, which employs hydrochloric acid, a relatively weaker acid than perchloric acid, when applied to used oil analysis.
- One school suggests that the D2896 method is better because the strong acid neutralizes strong and weak alkaline components in the oil, providing a more realistic measurement of the true base number, while D4739 only measures the strong alkaline components.
- The other school suggests that the strong acid used in D2896 reacts with weak alkaline wear metals in the oil, producing a falsely exaggerated base number, which could lead to an overextend oil drain interval. D4739 measures only the additive package, which is there to neutralize acids, making it a more accurate test for used oil analysis.
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