|Standards||ASTM D 482, ASTM D 874|
The ash content of engine oils enables conclusions to be drawn on potential oil additive deposit formation on hot engine parts. This is why the permissible ash content is listed in specifications.
A portion of the sample is heated in a muffle furnace at a set temperature to get rid of semi-volatiles, such as the base oil or fuel itself. These eventually burn away, leaving only a residue.
Sulfated ash determination is as the same as regular ash testing, with the added step of digestion in concentrated sulfuric acid - making it usable for greases and other matrices.
The amount of residue, measured gravimetrically, remaining following combustion at a known temperature.
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