Lubricant Additives & Specialty Chemicals | Manufacturer & Sourcing Partner | Jinzhou, China — Est. 2013
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Calculator ASTM D874

Sulfated Ash Contribution Calculator

Estimate the theoretical sulfated ash a metallic detergent or other metal-bearing additive contributes to a finished oil, per ASTM D874.

Additive
wt%

From the additive TDS (e.g. overbased Ca sulfonate ≈ 12–16% Ca).

wt%
Sulfated Ash

Select a metal and enter
metal content and treat rate.

Formula & Methodology (ASTM D874)
On ignition + sulfuric-acid treatment each metal ends up as its sulfate. Theoretical sulfated ash from metal content: additive ash (wt%) = metal (wt%) × F contribution (wt%) = treat rate (wt%) ÷ 100 × additive ash Metal → sulfate factors F (sulfate MW ÷ metal mass): Ca→CaSO4 3.40 Mg→MgSO4 4.95 Zn→ZnSO4 2.47 Ba→BaSO4 1.70 Na→Na2SO4 3.09 K→K2SO4 2.23

Theoretical value from metal content; measured ASTM D874 can differ slightly (boron, phosphorus and some metals form oxides/phosphates). Prefer the additive TDS ash figure when given.

Source: ASTM D874: Sulfated Ash from Lubricating Oils and Additives. Factors are stoichiometric (metal → sulfate).

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