The sulphate ash content of new and used lubricants changes as a result of factors such as metal abrasion or solid impurities (dust).
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.
Sulphate ash in lubricating greases consists of metallic soaps, inorganic thickening agents and other additives. They are altered by abrasion and impurities and allow conclusions to be drawn on matters such as bearing wear in comparison with new grease.