Mixed Cylinder Oil BN

BN of a mix of two cylinder oils (e.g., BN 70 + BN 140 topping-up): mass-weighted log-linear approximation.

Lubrication

Oil 1 BNmg KOH/gOil 1 mass in sumpkgOil 2 BNmg KOH/gOil 2 mass addedkg

Mixed BN: 90.0mg KOH/g

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Formula, assumptions, and limits

BN_\text{mix} = \frac{m_1 BN_1 + m_2 BN_2}{m_1 + m_2}

Symbol	Meaning	Unit
$BN$	Base Number	mg KOH/g
$m$	Oil mass	kg

Source: ASTM D2896 - TBN

In short

BN of a mix of two cylinder oils (e.

Learn the theory Cylinder Lubrication Systems: Two-Stroke Engines